Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

19 files changed, 3336 insertions, 0 deletions

diff --git a/test/chan/doubleselect.go b/test/chan/doubleselect.go
new file mode 100644
index 0000000..ff69dbe
--- /dev/null
+++ b/test/chan/doubleselect.go
@@ -0,0 +1,87 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test the situation in which two cases of a select can
+// both end up running. See http://codereview.appspot.com/180068.
+
+package main
+
+import (
+	"flag"
+	"runtime"
+)
+
+var iterations *int = flag.Int("n", 100000, "number of iterations")
+
+// sender sends a counter to one of four different channels. If two
+// cases both end up running in the same iteration, the same value will be sent
+// to two different channels.
+func sender(n int, c1, c2, c3, c4 chan<- int) {
+	defer close(c1)
+	defer close(c2)
+	defer close(c3)
+	defer close(c4)
+
+	for i := 0; i < n; i++ {
+		select {
+		case c1 <- i:
+		case c2 <- i:
+		case c3 <- i:
+		case c4 <- i:
+		}
+	}
+}
+
+// mux receives the values from sender and forwards them onto another channel.
+// It would be simpler to just have sender's four cases all be the same
+// channel, but this doesn't actually trigger the bug.
+func mux(out chan<- int, in <-chan int, done chan<- bool) {
+	for v := range in {
+		out <- v
+	}
+	done <- true
+}
+
+// recver gets a steam of values from the four mux's and checks for duplicates.
+func recver(in <-chan int) {
+	seen := make(map[int]bool)
+
+	for v := range in {
+		if _, ok := seen[v]; ok {
+			println("got duplicate value: ", v)
+			panic("fail")
+		}
+		seen[v] = true
+	}
+}
+
+func main() {
+	runtime.GOMAXPROCS(2)
+
+	flag.Parse()
+	c1 := make(chan int)
+	c2 := make(chan int)
+	c3 := make(chan int)
+	c4 := make(chan int)
+	done := make(chan bool)
+	cmux := make(chan int)
+	go sender(*iterations, c1, c2, c3, c4)
+	go mux(cmux, c1, done)
+	go mux(cmux, c2, done)
+	go mux(cmux, c3, done)
+	go mux(cmux, c4, done)
+	go func() {
+		<-done
+		<-done
+		<-done
+		<-done
+		close(cmux)
+	}()
+	// We keep the recver because it might catch more bugs in the future.
+	// However, the result of the bug linked to at the top is that we'll
+	// end up panicking with: "throw: bad g->status in ready".
+	recver(cmux)
+}
diff --git a/test/chan/fifo.go b/test/chan/fifo.go
new file mode 100644
index 0000000..0001bcf
--- /dev/null
+++ b/test/chan/fifo.go
@@ -0,0 +1,56 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that unbuffered channels act as pure fifos.
+
+package main
+
+import "os"
+
+const N = 10
+
+func AsynchFifo() {
+	ch := make(chan int, N)
+	for i := 0; i < N; i++ {
+		ch <- i
+	}
+	for i := 0; i < N; i++ {
+		if <-ch != i {
+			print("bad receive\n")
+			os.Exit(1)
+		}
+	}
+}
+
+func Chain(ch <-chan int, val int, in <-chan int, out chan<- int) {
+	<-in
+	if <-ch != val {
+		panic(val)
+	}
+	out <- 1
+}
+
+// thread together a daisy chain to read the elements in sequence
+func SynchFifo() {
+	ch := make(chan int)
+	in := make(chan int)
+	start := in
+	for i := 0; i < N; i++ {
+		out := make(chan int)
+		go Chain(ch, i, in, out)
+		in = out
+	}
+	start <- 0
+	for i := 0; i < N; i++ {
+		ch <- i
+	}
+	<-in
+}
+
+func main() {
+	AsynchFifo()
+	SynchFifo()
+}
diff --git a/test/chan/goroutines.go b/test/chan/goroutines.go
new file mode 100644
index 0000000..6ffae7d
--- /dev/null
+++ b/test/chan/goroutines.go
@@ -0,0 +1,41 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Torture test for goroutines.
+// Make a lot of goroutines, threaded together, and tear them down cleanly.
+
+package main
+
+import (
+	"os"
+	"strconv"
+)
+
+func f(left, right chan int) {
+	left <- <-right
+}
+
+func main() {
+	var n = 10000
+	if len(os.Args) > 1 {
+		var err error
+		n, err = strconv.Atoi(os.Args[1])
+		if err != nil {
+			print("bad arg\n")
+			os.Exit(1)
+		}
+	}
+	leftmost := make(chan int)
+	right := leftmost
+	left := leftmost
+	for i := 0; i < n; i++ {
+		right = make(chan int)
+		go f(left, right)
+		left = right
+	}
+	go func(c chan int) { c <- 1 }(right)
+	<-leftmost
+}
diff --git a/test/chan/nonblock.go b/test/chan/nonblock.go
new file mode 100644
index 0000000..7e3c0c7
--- /dev/null
+++ b/test/chan/nonblock.go
@@ -0,0 +1,282 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test channel operations that test for blocking.
+// Use several sizes and types of operands.
+
+package main
+
+import "runtime"
+import "time"
+
+func i32receiver(c chan int32, strobe chan bool) {
+	if <-c != 123 {
+		panic("i32 value")
+	}
+	strobe <- true
+}
+
+func i32sender(c chan int32, strobe chan bool) {
+	c <- 234
+	strobe <- true
+}
+
+func i64receiver(c chan int64, strobe chan bool) {
+	if <-c != 123456 {
+		panic("i64 value")
+	}
+	strobe <- true
+}
+
+func i64sender(c chan int64, strobe chan bool) {
+	c <- 234567
+	strobe <- true
+}
+
+func breceiver(c chan bool, strobe chan bool) {
+	if !<-c {
+		panic("b value")
+	}
+	strobe <- true
+}
+
+func bsender(c chan bool, strobe chan bool) {
+	c <- true
+	strobe <- true
+}
+
+func sreceiver(c chan string, strobe chan bool) {
+	if <-c != "hello" {
+		panic("s value")
+	}
+	strobe <- true
+}
+
+func ssender(c chan string, strobe chan bool) {
+	c <- "hello again"
+	strobe <- true
+}
+
+var ticker = time.Tick(10 * 1000) // 10 us
+func sleep() {
+	<-ticker
+	<-ticker
+	runtime.Gosched()
+	runtime.Gosched()
+	runtime.Gosched()
+}
+
+const maxTries = 10000 // Up to 100ms per test.
+
+func main() {
+	var i32 int32
+	var i64 int64
+	var b bool
+	var s string
+
+	var sync = make(chan bool)
+
+	for buffer := 0; buffer < 2; buffer++ {
+		c32 := make(chan int32, buffer)
+		c64 := make(chan int64, buffer)
+		cb := make(chan bool, buffer)
+		cs := make(chan string, buffer)
+
+		select {
+		case i32 = <-c32:
+			panic("blocked i32sender")
+		default:
+		}
+
+		select {
+		case i64 = <-c64:
+			panic("blocked i64sender")
+		default:
+		}
+
+		select {
+		case b = <-cb:
+			panic("blocked bsender")
+		default:
+		}
+
+		select {
+		case s = <-cs:
+			panic("blocked ssender")
+		default:
+		}
+
+		go i32receiver(c32, sync)
+		try := 0
+	Send32:
+		for {
+			select {
+			case c32 <- 123:
+				break Send32
+			default:
+				try++
+				if try > maxTries {
+					println("i32receiver buffer=", buffer)
+					panic("fail")
+				}
+				sleep()
+			}
+		}
+		<-sync
+
+		go i32sender(c32, sync)
+		if buffer > 0 {
+			<-sync
+		}
+		try = 0
+	Recv32:
+		for {
+			select {
+			case i32 = <-c32:
+				break Recv32
+			default:
+				try++
+				if try > maxTries {
+					println("i32sender buffer=", buffer)
+					panic("fail")
+				}
+				sleep()
+			}
+		}
+		if i32 != 234 {
+			panic("i32sender value")
+		}
+		if buffer == 0 {
+			<-sync
+		}
+
+		go i64receiver(c64, sync)
+		try = 0
+	Send64:
+		for {
+			select {
+			case c64 <- 123456:
+				break Send64
+			default:
+				try++
+				if try > maxTries {
+					panic("i64receiver")
+				}
+				sleep()
+			}
+		}
+		<-sync
+
+		go i64sender(c64, sync)
+		if buffer > 0 {
+			<-sync
+		}
+		try = 0
+	Recv64:
+		for {
+			select {
+			case i64 = <-c64:
+				break Recv64
+			default:
+				try++
+				if try > maxTries {
+					panic("i64sender")
+				}
+				sleep()
+			}
+		}
+		if i64 != 234567 {
+			panic("i64sender value")
+		}
+		if buffer == 0 {
+			<-sync
+		}
+
+		go breceiver(cb, sync)
+		try = 0
+	SendBool:
+		for {
+			select {
+			case cb <- true:
+				break SendBool
+			default:
+				try++
+				if try > maxTries {
+					panic("breceiver")
+				}
+				sleep()
+			}
+		}
+		<-sync
+
+		go bsender(cb, sync)
+		if buffer > 0 {
+			<-sync
+		}
+		try = 0
+	RecvBool:
+		for {
+			select {
+			case b = <-cb:
+				break RecvBool
+			default:
+				try++
+				if try > maxTries {
+					panic("bsender")
+				}
+				sleep()
+			}
+		}
+		if !b {
+			panic("bsender value")
+		}
+		if buffer == 0 {
+			<-sync
+		}
+
+		go sreceiver(cs, sync)
+		try = 0
+	SendString:
+		for {
+			select {
+			case cs <- "hello":
+				break SendString
+			default:
+				try++
+				if try > maxTries {
+					panic("sreceiver")
+				}
+				sleep()
+			}
+		}
+		<-sync
+
+		go ssender(cs, sync)
+		if buffer > 0 {
+			<-sync
+		}
+		try = 0
+	RecvString:
+		for {
+			select {
+			case s = <-cs:
+				break RecvString
+			default:
+				try++
+				if try > maxTries {
+					panic("ssender")
+				}
+				sleep()
+			}
+		}
+		if s != "hello again" {
+			panic("ssender value")
+		}
+		if buffer == 0 {
+			<-sync
+		}
+	}
+}
diff --git a/test/chan/perm.go b/test/chan/perm.go
new file mode 100644
index 0000000..0c96d92
--- /dev/null
+++ b/test/chan/perm.go
@@ -0,0 +1,70 @@
+// errorcheck
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test various correct and incorrect permutations of send-only,
+// receive-only, and bidirectional channels.
+// Does not compile.
+
+package main
+
+var (
+	cr <-chan int
+	cs chan<- int
+	c  chan int
+)
+
+func main() {
+	cr = c  // ok
+	cs = c  // ok
+	c = cr  // ERROR "illegal types|incompatible|cannot"
+	c = cs  // ERROR "illegal types|incompatible|cannot"
+	cr = cs // ERROR "illegal types|incompatible|cannot"
+	cs = cr // ERROR "illegal types|incompatible|cannot"
+
+	var n int
+	<-n    // ERROR "receive from non-chan|expected channel"
+	n <- 2 // ERROR "send to non-chan|must be channel"
+
+	c <- 0       // ok
+	<-c          // ok
+	x, ok := <-c // ok
+	_, _ = x, ok
+
+	cr <- 0      // ERROR "send"
+	<-cr         // ok
+	x, ok = <-cr // ok
+	_, _ = x, ok
+
+	cs <- 0      // ok
+	<-cs         // ERROR "receive"
+	x, ok = <-cs // ERROR "receive"
+	_, _ = x, ok
+
+	select {
+	case c <- 0: // ok
+	case x := <-c: // ok
+		_ = x
+
+	case cr <- 0: // ERROR "send"
+	case x := <-cr: // ok
+		_ = x
+
+	case cs <- 0: // ok
+	case x := <-cs: // ERROR "receive"
+		_ = x
+	}
+
+	for _ = range cs { // ERROR "receive"
+	}
+
+	for range cs { // ERROR "receive"
+	}
+
+	close(c)
+	close(cs)
+	close(cr) // ERROR "receive"
+	close(n)  // ERROR "invalid operation.*non-chan type|must be channel"
+}
diff --git a/test/chan/powser1.go b/test/chan/powser1.go
new file mode 100644
index 0000000..e999dde
--- /dev/null
+++ b/test/chan/powser1.go
@@ -0,0 +1,741 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test concurrency primitives: power series.
+
+// Power series package
+// A power series is a channel, along which flow rational
+// coefficients.  A denominator of zero signifies the end.
+// Original code in Newsqueak by Doug McIlroy.
+// See Squinting at Power Series by Doug McIlroy,
+//   https://swtch.com/~rsc/thread/squint.pdf
+
+package main
+
+import "os"
+
+type rat struct {
+	num, den int64 // numerator, denominator
+}
+
+func (u rat) pr() {
+	if u.den == 1 {
+		print(u.num)
+	} else {
+		print(u.num, "/", u.den)
+	}
+	print(" ")
+}
+
+func (u rat) eq(c rat) bool {
+	return u.num == c.num && u.den == c.den
+}
+
+type dch struct {
+	req chan int
+	dat chan rat
+	nam int
+}
+
+type dch2 [2]*dch
+
+var chnames string
+var chnameserial int
+var seqno int
+
+func mkdch() *dch {
+	c := chnameserial % len(chnames)
+	chnameserial++
+	d := new(dch)
+	d.req = make(chan int)
+	d.dat = make(chan rat)
+	d.nam = c
+	return d
+}
+
+func mkdch2() *dch2 {
+	d2 := new(dch2)
+	d2[0] = mkdch()
+	d2[1] = mkdch()
+	return d2
+}
+
+// split reads a single demand channel and replicates its
+// output onto two, which may be read at different rates.
+// A process is created at first demand for a rat and dies
+// after the rat has been sent to both outputs.
+
+// When multiple generations of split exist, the newest
+// will service requests on one channel, which is
+// always renamed to be out[0]; the oldest will service
+// requests on the other channel, out[1].  All generations but the
+// newest hold queued data that has already been sent to
+// out[0].  When data has finally been sent to out[1],
+// a signal on the release-wait channel tells the next newer
+// generation to begin servicing out[1].
+
+func dosplit(in *dch, out *dch2, wait chan int) {
+	both := false // do not service both channels
+
+	select {
+	case <-out[0].req:
+
+	case <-wait:
+		both = true
+		select {
+		case <-out[0].req:
+
+		case <-out[1].req:
+			out[0], out[1] = out[1], out[0]
+		}
+	}
+
+	seqno++
+	in.req <- seqno
+	release := make(chan int)
+	go dosplit(in, out, release)
+	dat := <-in.dat
+	out[0].dat <- dat
+	if !both {
+		<-wait
+	}
+	<-out[1].req
+	out[1].dat <- dat
+	release <- 0
+}
+
+func split(in *dch, out *dch2) {
+	release := make(chan int)
+	go dosplit(in, out, release)
+	release <- 0
+}
+
+func put(dat rat, out *dch) {
+	<-out.req
+	out.dat <- dat
+}
+
+func get(in *dch) rat {
+	seqno++
+	in.req <- seqno
+	return <-in.dat
+}
+
+// Get one rat from each of n demand channels
+
+func getn(in []*dch) []rat {
+	n := len(in)
+	if n != 2 {
+		panic("bad n in getn")
+	}
+	req := new([2]chan int)
+	dat := new([2]chan rat)
+	out := make([]rat, 2)
+	var i int
+	var it rat
+	for i = 0; i < n; i++ {
+		req[i] = in[i].req
+		dat[i] = nil
+	}
+	for n = 2 * n; n > 0; n-- {
+		seqno++
+
+		select {
+		case req[0] <- seqno:
+			dat[0] = in[0].dat
+			req[0] = nil
+		case req[1] <- seqno:
+			dat[1] = in[1].dat
+			req[1] = nil
+		case it = <-dat[0]:
+			out[0] = it
+			dat[0] = nil
+		case it = <-dat[1]:
+			out[1] = it
+			dat[1] = nil
+		}
+	}
+	return out
+}
+
+// Get one rat from each of 2 demand channels
+
+func get2(in0 *dch, in1 *dch) []rat {
+	return getn([]*dch{in0, in1})
+}
+
+func copy(in *dch, out *dch) {
+	for {
+		<-out.req
+		out.dat <- get(in)
+	}
+}
+
+func repeat(dat rat, out *dch) {
+	for {
+		put(dat, out)
+	}
+}
+
+type PS *dch    // power series
+type PS2 *[2]PS // pair of power series
+
+var Ones PS
+var Twos PS
+
+func mkPS() *dch {
+	return mkdch()
+}
+
+func mkPS2() *dch2 {
+	return mkdch2()
+}
+
+// Conventions
+// Upper-case for power series.
+// Lower-case for rationals.
+// Input variables: U,V,...
+// Output variables: ...,Y,Z
+
+// Integer gcd; needed for rational arithmetic
+
+func gcd(u, v int64) int64 {
+	if u < 0 {
+		return gcd(-u, v)
+	}
+	if u == 0 {
+		return v
+	}
+	return gcd(v%u, u)
+}
+
+// Make a rational from two ints and from one int
+
+func i2tor(u, v int64) rat {
+	g := gcd(u, v)
+	var r rat
+	if v > 0 {
+		r.num = u / g
+		r.den = v / g
+	} else {
+		r.num = -u / g
+		r.den = -v / g
+	}
+	return r
+}
+
+func itor(u int64) rat {
+	return i2tor(u, 1)
+}
+
+var zero rat
+var one rat
+
+// End mark and end test
+
+var finis rat
+
+func end(u rat) int64 {
+	if u.den == 0 {
+		return 1
+	}
+	return 0
+}
+
+// Operations on rationals
+
+func add(u, v rat) rat {
+	g := gcd(u.den, v.den)
+	return i2tor(u.num*(v.den/g)+v.num*(u.den/g), u.den*(v.den/g))
+}
+
+func mul(u, v rat) rat {
+	g1 := gcd(u.num, v.den)
+	g2 := gcd(u.den, v.num)
+	var r rat
+	r.num = (u.num / g1) * (v.num / g2)
+	r.den = (u.den / g2) * (v.den / g1)
+	return r
+}
+
+func neg(u rat) rat {
+	return i2tor(-u.num, u.den)
+}
+
+func sub(u, v rat) rat {
+	return add(u, neg(v))
+}
+
+func inv(u rat) rat { // invert a rat
+	if u.num == 0 {
+		panic("zero divide in inv")
+	}
+	return i2tor(u.den, u.num)
+}
+
+// print eval in floating point of PS at x=c to n terms
+func evaln(c rat, U PS, n int) {
+	xn := float64(1)
+	x := float64(c.num) / float64(c.den)
+	val := float64(0)
+	for i := 0; i < n; i++ {
+		u := get(U)
+		if end(u) != 0 {
+			break
+		}
+		val = val + x*float64(u.num)/float64(u.den)
+		xn = xn * x
+	}
+	print(val, "\n")
+}
+
+// Print n terms of a power series
+func printn(U PS, n int) {
+	done := false
+	for ; !done && n > 0; n-- {
+		u := get(U)
+		if end(u) != 0 {
+			done = true
+		} else {
+			u.pr()
+		}
+	}
+	print(("\n"))
+}
+
+// Evaluate n terms of power series U at x=c
+func eval(c rat, U PS, n int) rat {
+	if n == 0 {
+		return zero
+	}
+	y := get(U)
+	if end(y) != 0 {
+		return zero
+	}
+	return add(y, mul(c, eval(c, U, n-1)))
+}
+
+// Power-series constructors return channels on which power
+// series flow.  They start an encapsulated generator that
+// puts the terms of the series on the channel.
+
+// Make a pair of power series identical to a given power series
+
+func Split(U PS) *dch2 {
+	UU := mkdch2()
+	go split(U, UU)
+	return UU
+}
+
+// Add two power series
+func Add(U, V PS) PS {
+	Z := mkPS()
+	go func() {
+		var uv []rat
+		for {
+			<-Z.req
+			uv = get2(U, V)
+			switch end(uv[0]) + 2*end(uv[1]) {
+			case 0:
+				Z.dat <- add(uv[0], uv[1])
+			case 1:
+				Z.dat <- uv[1]
+				copy(V, Z)
+			case 2:
+				Z.dat <- uv[0]
+				copy(U, Z)
+			case 3:
+				Z.dat <- finis
+			}
+		}
+	}()
+	return Z
+}
+
+// Multiply a power series by a constant
+func Cmul(c rat, U PS) PS {
+	Z := mkPS()
+	go func() {
+		done := false
+		for !done {
+			<-Z.req
+			u := get(U)
+			if end(u) != 0 {
+				done = true
+			} else {
+				Z.dat <- mul(c, u)
+			}
+		}
+		Z.dat <- finis
+	}()
+	return Z
+}
+
+// Subtract
+
+func Sub(U, V PS) PS {
+	return Add(U, Cmul(neg(one), V))
+}
+
+// Multiply a power series by the monomial x^n
+
+func Monmul(U PS, n int) PS {
+	Z := mkPS()
+	go func() {
+		for ; n > 0; n-- {
+			put(zero, Z)
+		}
+		copy(U, Z)
+	}()
+	return Z
+}
+
+// Multiply by x
+
+func Xmul(U PS) PS {
+	return Monmul(U, 1)
+}
+
+func Rep(c rat) PS {
+	Z := mkPS()
+	go repeat(c, Z)
+	return Z
+}
+
+// Monomial c*x^n
+
+func Mon(c rat, n int) PS {
+	Z := mkPS()
+	go func() {
+		if c.num != 0 {
+			for ; n > 0; n = n - 1 {
+				put(zero, Z)
+			}
+			put(c, Z)
+		}
+		put(finis, Z)
+	}()
+	return Z
+}
+
+func Shift(c rat, U PS) PS {
+	Z := mkPS()
+	go func() {
+		put(c, Z)
+		copy(U, Z)
+	}()
+	return Z
+}
+
+// simple pole at 1: 1/(1-x) = 1 1 1 1 1 ...
+
+// Convert array of coefficients, constant term first
+// to a (finite) power series
+
+/*
+func Poly(a []rat) PS {
+	Z:=mkPS()
+	begin func(a []rat, Z PS) {
+		j:=0
+		done:=0
+		for j=len(a); !done&&j>0; j=j-1)
+			if(a[j-1].num!=0) done=1
+		i:=0
+		for(; i<j; i=i+1) put(a[i],Z)
+		put(finis,Z)
+	}()
+	return Z
+}
+*/
+
+// Multiply. The algorithm is
+//	let U = u + x*UU
+//	let V = v + x*VV
+//	then UV = u*v + x*(u*VV+v*UU) + x*x*UU*VV
+
+func Mul(U, V PS) PS {
+	Z := mkPS()
+	go func() {
+		<-Z.req
+		uv := get2(U, V)
+		if end(uv[0]) != 0 || end(uv[1]) != 0 {
+			Z.dat <- finis
+		} else {
+			Z.dat <- mul(uv[0], uv[1])
+			UU := Split(U)
+			VV := Split(V)
+			W := Add(Cmul(uv[0], VV[0]), Cmul(uv[1], UU[0]))
+			<-Z.req
+			Z.dat <- get(W)
+			copy(Add(W, Mul(UU[1], VV[1])), Z)
+		}
+	}()
+	return Z
+}
+
+// Differentiate
+
+func Diff(U PS) PS {
+	Z := mkPS()
+	go func() {
+		<-Z.req
+		u := get(U)
+		if end(u) == 0 {
+			done := false
+			for i := 1; !done; i++ {
+				u = get(U)
+				if end(u) != 0 {
+					done = true
+				} else {
+					Z.dat <- mul(itor(int64(i)), u)
+					<-Z.req
+				}
+			}
+		}
+		Z.dat <- finis
+	}()
+	return Z
+}
+
+// Integrate, with const of integration
+func Integ(c rat, U PS) PS {
+	Z := mkPS()
+	go func() {
+		put(c, Z)
+		done := false
+		for i := 1; !done; i++ {
+			<-Z.req
+			u := get(U)
+			if end(u) != 0 {
+				done = true
+			}
+			Z.dat <- mul(i2tor(1, int64(i)), u)
+		}
+		Z.dat <- finis
+	}()
+	return Z
+}
+
+// Binomial theorem (1+x)^c
+
+func Binom(c rat) PS {
+	Z := mkPS()
+	go func() {
+		n := 1
+		t := itor(1)
+		for c.num != 0 {
+			put(t, Z)
+			t = mul(mul(t, c), i2tor(1, int64(n)))
+			c = sub(c, one)
+			n++
+		}
+		put(finis, Z)
+	}()
+	return Z
+}
+
+// Reciprocal of a power series
+//	let U = u + x*UU
+//	let Z = z + x*ZZ
+//	(u+x*UU)*(z+x*ZZ) = 1
+//	z = 1/u
+//	u*ZZ + z*UU +x*UU*ZZ = 0
+//	ZZ = -UU*(z+x*ZZ)/u
+
+func Recip(U PS) PS {
+	Z := mkPS()
+	go func() {
+		ZZ := mkPS2()
+		<-Z.req
+		z := inv(get(U))
+		Z.dat <- z
+		split(Mul(Cmul(neg(z), U), Shift(z, ZZ[0])), ZZ)
+		copy(ZZ[1], Z)
+	}()
+	return Z
+}
+
+// Exponential of a power series with constant term 0
+// (nonzero constant term would make nonrational coefficients)
+// bug: the constant term is simply ignored
+//	Z = exp(U)
+//	DZ = Z*DU
+//	integrate to get Z
+
+func Exp(U PS) PS {
+	ZZ := mkPS2()
+	split(Integ(one, Mul(ZZ[0], Diff(U))), ZZ)
+	return ZZ[1]
+}
+
+// Substitute V for x in U, where the leading term of V is zero
+//	let U = u + x*UU
+//	let V = v + x*VV
+//	then S(U,V) = u + VV*S(V,UU)
+// bug: a nonzero constant term is ignored
+
+func Subst(U, V PS) PS {
+	Z := mkPS()
+	go func() {
+		VV := Split(V)
+		<-Z.req
+		u := get(U)
+		Z.dat <- u
+		if end(u) == 0 {
+			if end(get(VV[0])) != 0 {
+				put(finis, Z)
+			} else {
+				copy(Mul(VV[0], Subst(U, VV[1])), Z)
+			}
+		}
+	}()
+	return Z
+}
+
+// Monomial Substitution: U(c x^n)
+// Each Ui is multiplied by c^i and followed by n-1 zeros
+
+func MonSubst(U PS, c0 rat, n int) PS {
+	Z := mkPS()
+	go func() {
+		c := one
+		for {
+			<-Z.req
+			u := get(U)
+			Z.dat <- mul(u, c)
+			c = mul(c, c0)
+			if end(u) != 0 {
+				Z.dat <- finis
+				break
+			}
+			for i := 1; i < n; i++ {
+				<-Z.req
+				Z.dat <- zero
+			}
+		}
+	}()
+	return Z
+}
+
+func Init() {
+	chnameserial = -1
+	seqno = 0
+	chnames = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+	zero = itor(0)
+	one = itor(1)
+	finis = i2tor(1, 0)
+	Ones = Rep(one)
+	Twos = Rep(itor(2))
+}
+
+func check(U PS, c rat, count int, str string) {
+	for i := 0; i < count; i++ {
+		r := get(U)
+		if !r.eq(c) {
+			print("got: ")
+			r.pr()
+			print("should get ")
+			c.pr()
+			print("\n")
+			panic(str)
+		}
+	}
+}
+
+const N = 10
+
+func checka(U PS, a []rat, str string) {
+	for i := 0; i < N; i++ {
+		check(U, a[i], 1, str)
+	}
+}
+
+func main() {
+	Init()
+	if len(os.Args) > 1 { // print
+		print("Ones: ")
+		printn(Ones, 10)
+		print("Twos: ")
+		printn(Twos, 10)
+		print("Add: ")
+		printn(Add(Ones, Twos), 10)
+		print("Diff: ")
+		printn(Diff(Ones), 10)
+		print("Integ: ")
+		printn(Integ(zero, Ones), 10)
+		print("CMul: ")
+		printn(Cmul(neg(one), Ones), 10)
+		print("Sub: ")
+		printn(Sub(Ones, Twos), 10)
+		print("Mul: ")
+		printn(Mul(Ones, Ones), 10)
+		print("Exp: ")
+		printn(Exp(Ones), 15)
+		print("MonSubst: ")
+		printn(MonSubst(Ones, neg(one), 2), 10)
+		print("ATan: ")
+		printn(Integ(zero, MonSubst(Ones, neg(one), 2)), 10)
+	} else { // test
+		check(Ones, one, 5, "Ones")
+		check(Add(Ones, Ones), itor(2), 0, "Add Ones Ones") // 1 1 1 1 1
+		check(Add(Ones, Twos), itor(3), 0, "Add Ones Twos") // 3 3 3 3 3
+		a := make([]rat, N)
+		d := Diff(Ones)
+		for i := 0; i < N; i++ {
+			a[i] = itor(int64(i + 1))
+		}
+		checka(d, a, "Diff") // 1 2 3 4 5
+		in := Integ(zero, Ones)
+		a[0] = zero // integration constant
+		for i := 1; i < N; i++ {
+			a[i] = i2tor(1, int64(i))
+		}
+		checka(in, a, "Integ")                               // 0 1 1/2 1/3 1/4 1/5
+		check(Cmul(neg(one), Twos), itor(-2), 10, "CMul")    // -1 -1 -1 -1 -1
+		check(Sub(Ones, Twos), itor(-1), 0, "Sub Ones Twos") // -1 -1 -1 -1 -1
+		m := Mul(Ones, Ones)
+		for i := 0; i < N; i++ {
+			a[i] = itor(int64(i + 1))
+		}
+		checka(m, a, "Mul") // 1 2 3 4 5
+		e := Exp(Ones)
+		a[0] = itor(1)
+		a[1] = itor(1)
+		a[2] = i2tor(3, 2)
+		a[3] = i2tor(13, 6)
+		a[4] = i2tor(73, 24)
+		a[5] = i2tor(167, 40)
+		a[6] = i2tor(4051, 720)
+		a[7] = i2tor(37633, 5040)
+		a[8] = i2tor(43817, 4480)
+		a[9] = i2tor(4596553, 362880)
+		checka(e, a, "Exp") // 1 1 3/2 13/6 73/24
+		at := Integ(zero, MonSubst(Ones, neg(one), 2))
+		for c, i := 1, 0; i < N; i++ {
+			if i%2 == 0 {
+				a[i] = zero
+			} else {
+				a[i] = i2tor(int64(c), int64(i))
+				c *= -1
+			}
+		}
+		checka(at, a, "ATan") // 0 -1 0 -1/3 0 -1/5
+		/*
+			t := Revert(Integ(zero, MonSubst(Ones, neg(one), 2)))
+			a[0] = zero
+			a[1] = itor(1)
+			a[2] = zero
+			a[3] = i2tor(1,3)
+			a[4] = zero
+			a[5] = i2tor(2,15)
+			a[6] = zero
+			a[7] = i2tor(17,315)
+			a[8] = zero
+			a[9] = i2tor(62,2835)
+			checka(t, a, "Tan")  // 0 1 0 1/3 0 2/15
+		*/
+	}
+}
diff --git a/test/chan/powser2.go b/test/chan/powser2.go
new file mode 100644
index 0000000..72cbba8
--- /dev/null
+++ b/test/chan/powser2.go
@@ -0,0 +1,755 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test concurrency primitives: power series.
+
+// Like powser1.go but uses channels of interfaces.
+// Has not been cleaned up as much as powser1.go, to keep
+// it distinct and therefore a different test.
+
+// Power series package
+// A power series is a channel, along which flow rational
+// coefficients.  A denominator of zero signifies the end.
+// Original code in Newsqueak by Doug McIlroy.
+// See Squinting at Power Series by Doug McIlroy,
+//   https://swtch.com/~rsc/thread/squint.pdf
+
+package main
+
+import "os"
+
+type rat struct {
+	num, den int64 // numerator, denominator
+}
+
+type item interface {
+	pr()
+	eq(c item) bool
+}
+
+func (u *rat) pr() {
+	if u.den == 1 {
+		print(u.num)
+	} else {
+		print(u.num, "/", u.den)
+	}
+	print(" ")
+}
+
+func (u *rat) eq(c item) bool {
+	c1 := c.(*rat)
+	return u.num == c1.num && u.den == c1.den
+}
+
+type dch struct {
+	req chan int
+	dat chan item
+	nam int
+}
+
+type dch2 [2]*dch
+
+var chnames string
+var chnameserial int
+var seqno int
+
+func mkdch() *dch {
+	c := chnameserial % len(chnames)
+	chnameserial++
+	d := new(dch)
+	d.req = make(chan int)
+	d.dat = make(chan item)
+	d.nam = c
+	return d
+}
+
+func mkdch2() *dch2 {
+	d2 := new(dch2)
+	d2[0] = mkdch()
+	d2[1] = mkdch()
+	return d2
+}
+
+// split reads a single demand channel and replicates its
+// output onto two, which may be read at different rates.
+// A process is created at first demand for an item and dies
+// after the item has been sent to both outputs.
+
+// When multiple generations of split exist, the newest
+// will service requests on one channel, which is
+// always renamed to be out[0]; the oldest will service
+// requests on the other channel, out[1].  All generations but the
+// newest hold queued data that has already been sent to
+// out[0].  When data has finally been sent to out[1],
+// a signal on the release-wait channel tells the next newer
+// generation to begin servicing out[1].
+
+func dosplit(in *dch, out *dch2, wait chan int) {
+	both := false // do not service both channels
+
+	select {
+	case <-out[0].req:
+
+	case <-wait:
+		both = true
+		select {
+		case <-out[0].req:
+
+		case <-out[1].req:
+			out[0], out[1] = out[1], out[0]
+		}
+	}
+
+	seqno++
+	in.req <- seqno
+	release := make(chan int)
+	go dosplit(in, out, release)
+	dat := <-in.dat
+	out[0].dat <- dat
+	if !both {
+		<-wait
+	}
+	<-out[1].req
+	out[1].dat <- dat
+	release <- 0
+}
+
+func split(in *dch, out *dch2) {
+	release := make(chan int)
+	go dosplit(in, out, release)
+	release <- 0
+}
+
+func put(dat item, out *dch) {
+	<-out.req
+	out.dat <- dat
+}
+
+func get(in *dch) *rat {
+	seqno++
+	in.req <- seqno
+	return (<-in.dat).(*rat)
+}
+
+// Get one item from each of n demand channels
+
+func getn(in []*dch) []item {
+	n := len(in)
+	if n != 2 {
+		panic("bad n in getn")
+	}
+	req := make([]chan int, 2)
+	dat := make([]chan item, 2)
+	out := make([]item, 2)
+	var i int
+	var it item
+	for i = 0; i < n; i++ {
+		req[i] = in[i].req
+		dat[i] = nil
+	}
+	for n = 2 * n; n > 0; n-- {
+		seqno++
+
+		select {
+		case req[0] <- seqno:
+			dat[0] = in[0].dat
+			req[0] = nil
+		case req[1] <- seqno:
+			dat[1] = in[1].dat
+			req[1] = nil
+		case it = <-dat[0]:
+			out[0] = it
+			dat[0] = nil
+		case it = <-dat[1]:
+			out[1] = it
+			dat[1] = nil
+		}
+	}
+	return out
+}
+
+// Get one item from each of 2 demand channels
+
+func get2(in0 *dch, in1 *dch) []item {
+	return getn([]*dch{in0, in1})
+}
+
+func copy(in *dch, out *dch) {
+	for {
+		<-out.req
+		out.dat <- get(in)
+	}
+}
+
+func repeat(dat item, out *dch) {
+	for {
+		put(dat, out)
+	}
+}
+
+type PS *dch    // power series
+type PS2 *[2]PS // pair of power series
+
+var Ones PS
+var Twos PS
+
+func mkPS() *dch {
+	return mkdch()
+}
+
+func mkPS2() *dch2 {
+	return mkdch2()
+}
+
+// Conventions
+// Upper-case for power series.
+// Lower-case for rationals.
+// Input variables: U,V,...
+// Output variables: ...,Y,Z
+
+// Integer gcd; needed for rational arithmetic
+
+func gcd(u, v int64) int64 {
+	if u < 0 {
+		return gcd(-u, v)
+	}
+	if u == 0 {
+		return v
+	}
+	return gcd(v%u, u)
+}
+
+// Make a rational from two ints and from one int
+
+func i2tor(u, v int64) *rat {
+	g := gcd(u, v)
+	r := new(rat)
+	if v > 0 {
+		r.num = u / g
+		r.den = v / g
+	} else {
+		r.num = -u / g
+		r.den = -v / g
+	}
+	return r
+}
+
+func itor(u int64) *rat {
+	return i2tor(u, 1)
+}
+
+var zero *rat
+var one *rat
+
+// End mark and end test
+
+var finis *rat
+
+func end(u *rat) int64 {
+	if u.den == 0 {
+		return 1
+	}
+	return 0
+}
+
+// Operations on rationals
+
+func add(u, v *rat) *rat {
+	g := gcd(u.den, v.den)
+	return i2tor(u.num*(v.den/g)+v.num*(u.den/g), u.den*(v.den/g))
+}
+
+func mul(u, v *rat) *rat {
+	g1 := gcd(u.num, v.den)
+	g2 := gcd(u.den, v.num)
+	r := new(rat)
+	r.num = (u.num / g1) * (v.num / g2)
+	r.den = (u.den / g2) * (v.den / g1)
+	return r
+}
+
+func neg(u *rat) *rat {
+	return i2tor(-u.num, u.den)
+}
+
+func sub(u, v *rat) *rat {
+	return add(u, neg(v))
+}
+
+func inv(u *rat) *rat { // invert a rat
+	if u.num == 0 {
+		panic("zero divide in inv")
+	}
+	return i2tor(u.den, u.num)
+}
+
+// print eval in floating point of PS at x=c to n terms
+func Evaln(c *rat, U PS, n int) {
+	xn := float64(1)
+	x := float64(c.num) / float64(c.den)
+	val := float64(0)
+	for i := 0; i < n; i++ {
+		u := get(U)
+		if end(u) != 0 {
+			break
+		}
+		val = val + x*float64(u.num)/float64(u.den)
+		xn = xn * x
+	}
+	print(val, "\n")
+}
+
+// Print n terms of a power series
+func Printn(U PS, n int) {
+	done := false
+	for ; !done && n > 0; n-- {
+		u := get(U)
+		if end(u) != 0 {
+			done = true
+		} else {
+			u.pr()
+		}
+	}
+	print(("\n"))
+}
+
+func Print(U PS) {
+	Printn(U, 1000000000)
+}
+
+// Evaluate n terms of power series U at x=c
+func eval(c *rat, U PS, n int) *rat {
+	if n == 0 {
+		return zero
+	}
+	y := get(U)
+	if end(y) != 0 {
+		return zero
+	}
+	return add(y, mul(c, eval(c, U, n-1)))
+}
+
+// Power-series constructors return channels on which power
+// series flow.  They start an encapsulated generator that
+// puts the terms of the series on the channel.
+
+// Make a pair of power series identical to a given power series
+
+func Split(U PS) *dch2 {
+	UU := mkdch2()
+	go split(U, UU)
+	return UU
+}
+
+// Add two power series
+func Add(U, V PS) PS {
+	Z := mkPS()
+	go func(U, V, Z PS) {
+		var uv []item
+		for {
+			<-Z.req
+			uv = get2(U, V)
+			switch end(uv[0].(*rat)) + 2*end(uv[1].(*rat)) {
+			case 0:
+				Z.dat <- add(uv[0].(*rat), uv[1].(*rat))
+			case 1:
+				Z.dat <- uv[1]
+				copy(V, Z)
+			case 2:
+				Z.dat <- uv[0]
+				copy(U, Z)
+			case 3:
+				Z.dat <- finis
+			}
+		}
+	}(U, V, Z)
+	return Z
+}
+
+// Multiply a power series by a constant
+func Cmul(c *rat, U PS) PS {
+	Z := mkPS()
+	go func(c *rat, U, Z PS) {
+		done := false
+		for !done {
+			<-Z.req
+			u := get(U)
+			if end(u) != 0 {
+				done = true
+			} else {
+				Z.dat <- mul(c, u)
+			}
+		}
+		Z.dat <- finis
+	}(c, U, Z)
+	return Z
+}
+
+// Subtract
+
+func Sub(U, V PS) PS {
+	return Add(U, Cmul(neg(one), V))
+}
+
+// Multiply a power series by the monomial x^n
+
+func Monmul(U PS, n int) PS {
+	Z := mkPS()
+	go func(n int, U PS, Z PS) {
+		for ; n > 0; n-- {
+			put(zero, Z)
+		}
+		copy(U, Z)
+	}(n, U, Z)
+	return Z
+}
+
+// Multiply by x
+
+func Xmul(U PS) PS {
+	return Monmul(U, 1)
+}
+
+func Rep(c *rat) PS {
+	Z := mkPS()
+	go repeat(c, Z)
+	return Z
+}
+
+// Monomial c*x^n
+
+func Mon(c *rat, n int) PS {
+	Z := mkPS()
+	go func(c *rat, n int, Z PS) {
+		if c.num != 0 {
+			for ; n > 0; n = n - 1 {
+				put(zero, Z)
+			}
+			put(c, Z)
+		}
+		put(finis, Z)
+	}(c, n, Z)
+	return Z
+}
+
+func Shift(c *rat, U PS) PS {
+	Z := mkPS()
+	go func(c *rat, U, Z PS) {
+		put(c, Z)
+		copy(U, Z)
+	}(c, U, Z)
+	return Z
+}
+
+// simple pole at 1: 1/(1-x) = 1 1 1 1 1 ...
+
+// Convert array of coefficients, constant term first
+// to a (finite) power series
+
+/*
+func Poly(a [] *rat) PS{
+	Z:=mkPS()
+	begin func(a [] *rat, Z PS){
+		j:=0
+		done:=0
+		for j=len(a); !done&&j>0; j=j-1)
+			if(a[j-1].num!=0) done=1
+		i:=0
+		for(; i<j; i=i+1) put(a[i],Z)
+		put(finis,Z)
+	}()
+	return Z
+}
+*/
+
+// Multiply. The algorithm is
+//	let U = u + x*UU
+//	let V = v + x*VV
+//	then UV = u*v + x*(u*VV+v*UU) + x*x*UU*VV
+
+func Mul(U, V PS) PS {
+	Z := mkPS()
+	go func(U, V, Z PS) {
+		<-Z.req
+		uv := get2(U, V)
+		if end(uv[0].(*rat)) != 0 || end(uv[1].(*rat)) != 0 {
+			Z.dat <- finis
+		} else {
+			Z.dat <- mul(uv[0].(*rat), uv[1].(*rat))
+			UU := Split(U)
+			VV := Split(V)
+			W := Add(Cmul(uv[0].(*rat), VV[0]), Cmul(uv[1].(*rat), UU[0]))
+			<-Z.req
+			Z.dat <- get(W)
+			copy(Add(W, Mul(UU[1], VV[1])), Z)
+		}
+	}(U, V, Z)
+	return Z
+}
+
+// Differentiate
+
+func Diff(U PS) PS {
+	Z := mkPS()
+	go func(U, Z PS) {
+		<-Z.req
+		u := get(U)
+		if end(u) == 0 {
+			done := false
+			for i := 1; !done; i++ {
+				u = get(U)
+				if end(u) != 0 {
+					done = true
+				} else {
+					Z.dat <- mul(itor(int64(i)), u)
+					<-Z.req
+				}
+			}
+		}
+		Z.dat <- finis
+	}(U, Z)
+	return Z
+}
+
+// Integrate, with const of integration
+func Integ(c *rat, U PS) PS {
+	Z := mkPS()
+	go func(c *rat, U, Z PS) {
+		put(c, Z)
+		done := false
+		for i := 1; !done; i++ {
+			<-Z.req
+			u := get(U)
+			if end(u) != 0 {
+				done = true
+			}
+			Z.dat <- mul(i2tor(1, int64(i)), u)
+		}
+		Z.dat <- finis
+	}(c, U, Z)
+	return Z
+}
+
+// Binomial theorem (1+x)^c
+
+func Binom(c *rat) PS {
+	Z := mkPS()
+	go func(c *rat, Z PS) {
+		n := 1
+		t := itor(1)
+		for c.num != 0 {
+			put(t, Z)
+			t = mul(mul(t, c), i2tor(1, int64(n)))
+			c = sub(c, one)
+			n++
+		}
+		put(finis, Z)
+	}(c, Z)
+	return Z
+}
+
+// Reciprocal of a power series
+//	let U = u + x*UU
+//	let Z = z + x*ZZ
+//	(u+x*UU)*(z+x*ZZ) = 1
+//	z = 1/u
+//	u*ZZ + z*UU +x*UU*ZZ = 0
+//	ZZ = -UU*(z+x*ZZ)/u
+
+func Recip(U PS) PS {
+	Z := mkPS()
+	go func(U, Z PS) {
+		ZZ := mkPS2()
+		<-Z.req
+		z := inv(get(U))
+		Z.dat <- z
+		split(Mul(Cmul(neg(z), U), Shift(z, ZZ[0])), ZZ)
+		copy(ZZ[1], Z)
+	}(U, Z)
+	return Z
+}
+
+// Exponential of a power series with constant term 0
+// (nonzero constant term would make nonrational coefficients)
+// bug: the constant term is simply ignored
+//	Z = exp(U)
+//	DZ = Z*DU
+//	integrate to get Z
+
+func Exp(U PS) PS {
+	ZZ := mkPS2()
+	split(Integ(one, Mul(ZZ[0], Diff(U))), ZZ)
+	return ZZ[1]
+}
+
+// Substitute V for x in U, where the leading term of V is zero
+//	let U = u + x*UU
+//	let V = v + x*VV
+//	then S(U,V) = u + VV*S(V,UU)
+// bug: a nonzero constant term is ignored
+
+func Subst(U, V PS) PS {
+	Z := mkPS()
+	go func(U, V, Z PS) {
+		VV := Split(V)
+		<-Z.req
+		u := get(U)
+		Z.dat <- u
+		if end(u) == 0 {
+			if end(get(VV[0])) != 0 {
+				put(finis, Z)
+			} else {
+				copy(Mul(VV[0], Subst(U, VV[1])), Z)
+			}
+		}
+	}(U, V, Z)
+	return Z
+}
+
+// Monomial Substitution: U(c x^n)
+// Each Ui is multiplied by c^i and followed by n-1 zeros
+
+func MonSubst(U PS, c0 *rat, n int) PS {
+	Z := mkPS()
+	go func(U, Z PS, c0 *rat, n int) {
+		c := one
+		for {
+			<-Z.req
+			u := get(U)
+			Z.dat <- mul(u, c)
+			c = mul(c, c0)
+			if end(u) != 0 {
+				Z.dat <- finis
+				break
+			}
+			for i := 1; i < n; i++ {
+				<-Z.req
+				Z.dat <- zero
+			}
+		}
+	}(U, Z, c0, n)
+	return Z
+}
+
+func Init() {
+	chnameserial = -1
+	seqno = 0
+	chnames = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+	zero = itor(0)
+	one = itor(1)
+	finis = i2tor(1, 0)
+	Ones = Rep(one)
+	Twos = Rep(itor(2))
+}
+
+func check(U PS, c *rat, count int, str string) {
+	for i := 0; i < count; i++ {
+		r := get(U)
+		if !r.eq(c) {
+			print("got: ")
+			r.pr()
+			print("should get ")
+			c.pr()
+			print("\n")
+			panic(str)
+		}
+	}
+}
+
+const N = 10
+
+func checka(U PS, a []*rat, str string) {
+	for i := 0; i < N; i++ {
+		check(U, a[i], 1, str)
+	}
+}
+
+func main() {
+	Init()
+	if len(os.Args) > 1 { // print
+		print("Ones: ")
+		Printn(Ones, 10)
+		print("Twos: ")
+		Printn(Twos, 10)
+		print("Add: ")
+		Printn(Add(Ones, Twos), 10)
+		print("Diff: ")
+		Printn(Diff(Ones), 10)
+		print("Integ: ")
+		Printn(Integ(zero, Ones), 10)
+		print("CMul: ")
+		Printn(Cmul(neg(one), Ones), 10)
+		print("Sub: ")
+		Printn(Sub(Ones, Twos), 10)
+		print("Mul: ")
+		Printn(Mul(Ones, Ones), 10)
+		print("Exp: ")
+		Printn(Exp(Ones), 15)
+		print("MonSubst: ")
+		Printn(MonSubst(Ones, neg(one), 2), 10)
+		print("ATan: ")
+		Printn(Integ(zero, MonSubst(Ones, neg(one), 2)), 10)
+	} else { // test
+		check(Ones, one, 5, "Ones")
+		check(Add(Ones, Ones), itor(2), 0, "Add Ones Ones") // 1 1 1 1 1
+		check(Add(Ones, Twos), itor(3), 0, "Add Ones Twos") // 3 3 3 3 3
+		a := make([]*rat, N)
+		d := Diff(Ones)
+		for i := 0; i < N; i++ {
+			a[i] = itor(int64(i + 1))
+		}
+		checka(d, a, "Diff") // 1 2 3 4 5
+		in := Integ(zero, Ones)
+		a[0] = zero // integration constant
+		for i := 1; i < N; i++ {
+			a[i] = i2tor(1, int64(i))
+		}
+		checka(in, a, "Integ")                               // 0 1 1/2 1/3 1/4 1/5
+		check(Cmul(neg(one), Twos), itor(-2), 10, "CMul")    // -1 -1 -1 -1 -1
+		check(Sub(Ones, Twos), itor(-1), 0, "Sub Ones Twos") // -1 -1 -1 -1 -1
+		m := Mul(Ones, Ones)
+		for i := 0; i < N; i++ {
+			a[i] = itor(int64(i + 1))
+		}
+		checka(m, a, "Mul") // 1 2 3 4 5
+		e := Exp(Ones)
+		a[0] = itor(1)
+		a[1] = itor(1)
+		a[2] = i2tor(3, 2)
+		a[3] = i2tor(13, 6)
+		a[4] = i2tor(73, 24)
+		a[5] = i2tor(167, 40)
+		a[6] = i2tor(4051, 720)
+		a[7] = i2tor(37633, 5040)
+		a[8] = i2tor(43817, 4480)
+		a[9] = i2tor(4596553, 362880)
+		checka(e, a, "Exp") // 1 1 3/2 13/6 73/24
+		at := Integ(zero, MonSubst(Ones, neg(one), 2))
+		for c, i := 1, 0; i < N; i++ {
+			if i%2 == 0 {
+				a[i] = zero
+			} else {
+				a[i] = i2tor(int64(c), int64(i))
+				c *= -1
+			}
+		}
+		checka(at, a, "ATan") // 0 -1 0 -1/3 0 -1/5
+		/*
+			t := Revert(Integ(zero, MonSubst(Ones, neg(one), 2)))
+			a[0] = zero
+			a[1] = itor(1)
+			a[2] = zero
+			a[3] = i2tor(1,3)
+			a[4] = zero
+			a[5] = i2tor(2,15)
+			a[6] = zero
+			a[7] = i2tor(17,315)
+			a[8] = zero
+			a[9] = i2tor(62,2835)
+			checka(t, a, "Tan")  // 0 1 0 1/3 0 2/15
+		*/
+	}
+}
diff --git a/test/chan/select.go b/test/chan/select.go
new file mode 100644
index 0000000..38fa7e1
--- /dev/null
+++ b/test/chan/select.go
@@ -0,0 +1,58 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test simple select.
+
+package main
+
+var counter uint
+var shift uint
+
+func GetValue() uint {
+	counter++
+	return 1 << shift
+}
+
+func Send(a, b chan uint) int {
+	var i int
+
+LOOP:
+	for {
+		select {
+		case a <- GetValue():
+			i++
+			a = nil
+		case b <- GetValue():
+			i++
+			b = nil
+		default:
+			break LOOP
+		}
+		shift++
+	}
+	return i
+}
+
+func main() {
+	a := make(chan uint, 1)
+	b := make(chan uint, 1)
+	if v := Send(a, b); v != 2 {
+		println("Send returned", v, "!= 2")
+		panic("fail")
+	}
+	if av, bv := <-a, <-b; av|bv != 3 {
+		println("bad values", av, bv)
+		panic("fail")
+	}
+	if v := Send(a, nil); v != 1 {
+		println("Send returned", v, "!= 1")
+		panic("fail")
+	}
+	if counter != 10 {
+		println("counter is", counter, "!= 10")
+		panic("fail")
+	}
+}
diff --git a/test/chan/select2.go b/test/chan/select2.go
new file mode 100644
index 0000000..31e27d7
--- /dev/null
+++ b/test/chan/select2.go
@@ -0,0 +1,54 @@
+// run
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that selects do not consume undue memory.
+
+package main
+
+import "runtime"
+
+func sender(c chan int, n int) {
+	for i := 0; i < n; i++ {
+		c <- 1
+	}
+}
+
+func receiver(c, dummy chan int, n int) {
+	for i := 0; i < n; i++ {
+		select {
+		case <-c:
+			// nothing
+		case <-dummy:
+			panic("dummy")
+		}
+	}
+}
+
+func main() {
+	runtime.MemProfileRate = 0
+
+	c := make(chan int)
+	dummy := make(chan int)
+
+	// warm up
+	go sender(c, 100000)
+	receiver(c, dummy, 100000)
+	runtime.GC()
+	memstats := new(runtime.MemStats)
+	runtime.ReadMemStats(memstats)
+	alloc := memstats.Alloc
+
+	// second time shouldn't increase footprint by much
+	go sender(c, 100000)
+	receiver(c, dummy, 100000)
+	runtime.GC()
+	runtime.ReadMemStats(memstats)
+
+	// Be careful to avoid wraparound.
+	if memstats.Alloc > alloc && memstats.Alloc-alloc > 1.1e5 {
+		println("BUG: too much memory for 100,000 selects:", memstats.Alloc-alloc)
+	}
+}
diff --git a/test/chan/select3.go b/test/chan/select3.go
new file mode 100644
index 0000000..dd14c73
--- /dev/null
+++ b/test/chan/select3.go
@@ -0,0 +1,226 @@
+// run
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test the semantics of the select statement
+// for basic empty/non-empty cases.
+
+package main
+
+import "time"
+
+const always = "function did not"
+const never = "function did"
+
+func unreachable() {
+	panic("control flow shouldn't reach here")
+}
+
+// Calls f and verifies that f always/never panics depending on signal.
+func testPanic(signal string, f func()) {
+	defer func() {
+		s := never
+		if recover() != nil {
+			s = always // f panicked
+		}
+		if s != signal {
+			panic(signal + " panic")
+		}
+	}()
+	f()
+}
+
+// Calls f and empirically verifies that f always/never blocks depending on signal.
+func testBlock(signal string, f func()) {
+	c := make(chan string)
+	go func() {
+		f()
+		c <- never // f didn't block
+	}()
+	go func() {
+		if signal == never {
+			// Wait a long time to make sure that we don't miss our window by accident on a slow machine.
+			time.Sleep(10 * time.Second)
+		} else {
+			// Wait as short a time as we can without false negatives.
+			// 10ms should be long enough to catch most failures.
+			time.Sleep(10 * time.Millisecond)
+		}
+		c <- always // f blocked always
+	}()
+	if <-c != signal {
+		panic(signal + " block")
+	}
+}
+
+func main() {
+	const async = 1 // asynchronous channels
+	var nilch chan int
+	closedch := make(chan int)
+	close(closedch)
+
+	// sending/receiving from a nil channel blocks
+	testBlock(always, func() {
+		nilch <- 7
+	})
+	testBlock(always, func() {
+		<-nilch
+	})
+
+	// sending/receiving from a nil channel inside a select is never selected
+	testPanic(never, func() {
+		select {
+		case nilch <- 7:
+			unreachable()
+		default:
+		}
+	})
+	testPanic(never, func() {
+		select {
+		case <-nilch:
+			unreachable()
+		default:
+		}
+	})
+
+	// sending to an async channel with free buffer space never blocks
+	testBlock(never, func() {
+		ch := make(chan int, async)
+		ch <- 7
+	})
+
+	// receiving from a closed channel never blocks
+	testBlock(never, func() {
+		for i := 0; i < 10; i++ {
+			if <-closedch != 0 {
+				panic("expected zero value when reading from closed channel")
+			}
+			if x, ok := <-closedch; x != 0 || ok {
+				println("closedch:", x, ok)
+				panic("expected 0, false from closed channel")
+			}
+		}
+	})
+
+	// sending to a closed channel panics.
+	testPanic(always, func() {
+		closedch <- 7
+	})
+
+	// receiving from a non-ready channel always blocks
+	testBlock(always, func() {
+		ch := make(chan int)
+		<-ch
+	})
+
+	// empty selects always block
+	testBlock(always, func() {
+		select {}
+	})
+
+	// selects with only nil channels always block
+	testBlock(always, func() {
+		select {
+		case <-nilch:
+			unreachable()
+		}
+	})
+	testBlock(always, func() {
+		select {
+		case nilch <- 7:
+			unreachable()
+		}
+	})
+	testBlock(always, func() {
+		select {
+		case <-nilch:
+			unreachable()
+		case nilch <- 7:
+			unreachable()
+		}
+	})
+
+	// selects with non-ready non-nil channels always block
+	testBlock(always, func() {
+		ch := make(chan int)
+		select {
+		case <-ch:
+			unreachable()
+		}
+	})
+
+	// selects with default cases don't block
+	testBlock(never, func() {
+		select {
+		default:
+		}
+	})
+	testBlock(never, func() {
+		select {
+		case <-nilch:
+			unreachable()
+		default:
+		}
+	})
+	testBlock(never, func() {
+		select {
+		case nilch <- 7:
+			unreachable()
+		default:
+		}
+	})
+
+	// selects with ready channels don't block
+	testBlock(never, func() {
+		ch := make(chan int, async)
+		select {
+		case ch <- 7:
+		default:
+			unreachable()
+		}
+	})
+	testBlock(never, func() {
+		ch := make(chan int, async)
+		ch <- 7
+		select {
+		case <-ch:
+		default:
+			unreachable()
+		}
+	})
+
+	// selects with closed channels behave like ordinary operations
+	testBlock(never, func() {
+		select {
+		case <-closedch:
+		}
+	})
+	testBlock(never, func() {
+		select {
+		case x := (<-closedch):
+			_ = x
+		}
+	})
+	testBlock(never, func() {
+		select {
+		case x, ok := (<-closedch):
+			_, _ = x, ok
+		}
+	})
+	testPanic(always, func() {
+		select {
+		case closedch <- 7:
+		}
+	})
+
+	// select should not get confused if it sees itself
+	testBlock(always, func() {
+		c := make(chan int)
+		select {
+		case c <- 1:
+		case <-c:
+		}
+	})
+}
diff --git a/test/chan/select4.go b/test/chan/select4.go
new file mode 100644
index 0000000..5003640
--- /dev/null
+++ b/test/chan/select4.go
@@ -0,0 +1,31 @@
+// run
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file
+
+// Test that a select statement proceeds when a value is ready.
+
+package main
+
+func f() *int {
+	println("BUG: called f")
+	return new(int)
+}
+
+func main() {
+	var x struct {
+		a int
+	}
+	c := make(chan int, 1)
+	c1 := make(chan int)
+	c <- 42
+	select {
+	case *f() = <-c1:
+		// nothing
+	case x.a = <-c:
+		if x.a != 42 {
+			println("BUG:", x.a)
+		}
+	}
+}
diff --git a/test/chan/select5.go b/test/chan/select5.go
new file mode 100644
index 0000000..8b98c3a
--- /dev/null
+++ b/test/chan/select5.go
@@ -0,0 +1,481 @@
+// runoutput
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Generate test of channel operations and simple selects.
+// The output of this program is compiled and run to do the
+// actual test.
+
+// Each test does only one real send or receive at a time, but phrased
+// in various ways that the compiler may or may not rewrite
+// into simpler expressions.
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"text/template"
+)
+
+func main() {
+	out := bufio.NewWriter(os.Stdout)
+	fmt.Fprintln(out, header)
+	a := new(arg)
+
+	// Generate each test as a separate function to avoid
+	// hitting the gc optimizer with one enormous function.
+	// If we name all the functions init we don't have to
+	// maintain a list of which ones to run.
+	do := func(t *template.Template) {
+		for ; next(); a.reset() {
+			fmt.Fprintln(out, `func init() {`)
+			run(t, a, out)
+			fmt.Fprintln(out, `}`)
+		}
+	}
+
+	do(recv)
+	do(send)
+	do(recvOrder)
+	do(sendOrder)
+	do(nonblock)
+
+	fmt.Fprintln(out, "//", a.nreset, "cases")
+	out.Flush()
+}
+
+func run(t *template.Template, a interface{}, out io.Writer) {
+	if err := t.Execute(out, a); err != nil {
+		panic(err)
+	}
+}
+
+type arg struct {
+	def    bool
+	nreset int
+}
+
+func (a *arg) Maybe() bool {
+	return maybe()
+}
+
+func (a *arg) MaybeDefault() bool {
+	if a.def {
+		return false
+	}
+	a.def = maybe()
+	return a.def
+}
+
+func (a *arg) MustDefault() bool {
+	return !a.def
+}
+
+func (a *arg) reset() {
+	a.def = false
+	a.nreset++
+}
+
+const header = `// GENERATED BY select5.go; DO NOT EDIT
+
+package main
+
+// channel is buffered so test is single-goroutine.
+// we are not interested in the concurrency aspects
+// of select, just testing that the right calls happen.
+var c = make(chan int, 1)
+var nilch chan int
+var n = 1
+var x int
+var i interface{}
+var dummy = make(chan int)
+var m = make(map[int]int)
+var order = 0
+
+func f(p *int) *int {
+	return p
+}
+
+// check order of operations by ensuring that
+// successive calls to checkorder have increasing o values.
+func checkorder(o int) {
+	if o <= order {
+		println("invalid order", o, "after", order)
+		panic("order")
+	}
+	order = o
+}
+
+func fc(c chan int, o int) chan int {
+	checkorder(o)
+	return c
+}
+
+func fp(p *int, o int) *int {
+	checkorder(o)
+	return p
+}
+
+func fn(n, o int) int {
+	checkorder(o)
+	return n
+}
+
+func die(x int) {
+	println("have", x, "want", n)
+	panic("chan")
+}
+
+func main() {
+	// everything happens in init funcs
+}
+`
+
+func parse(name, s string) *template.Template {
+	t, err := template.New(name).Parse(s)
+	if err != nil {
+		panic(fmt.Sprintf("%q: %s", name, err))
+	}
+	return t
+}
+
+var recv = parse("recv", `
+	{{/*  Send n, receive it one way or another into x, check that they match. */}}
+	c <- n
+	{{if .Maybe}}
+	x = <-c
+	{{else}}
+	select {
+	{{/*  Blocking or non-blocking, before the receive. */}}
+	{{/*  The compiler implements two-case select where one is default with custom code, */}}
+	{{/*  so test the default branch both before and after the send. */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Receive from c.  Different cases are direct, indirect, :=, interface, and map assignment. */}}
+	{{if .Maybe}}
+	case x = <-c:
+	{{else}}{{if .Maybe}}
+	case *f(&x) = <-c:
+	{{else}}{{if .Maybe}}
+	case y := <-c:
+		x = y
+	{{else}}{{if .Maybe}}
+	case i = <-c:
+		x = i.(int)
+	{{else}}
+	case m[13] = <-c:
+		x = m[13]
+	{{end}}{{end}}{{end}}{{end}}
+	{{/*  Blocking or non-blocking again, after the receive. */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Dummy send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case dummy <- 1:
+		panic("dummy send")
+	{{end}}
+	{{if .Maybe}}
+	case <-dummy:
+		panic("dummy receive")
+	{{end}}
+	{{/*  Nil channel send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case nilch <- 1:
+		panic("nilch send")
+	{{end}}
+	{{if .Maybe}}
+	case <-nilch:
+		panic("nilch recv")
+	{{end}}
+	}
+	{{end}}
+	if x != n {
+		die(x)
+	}
+	n++
+`)
+
+var recvOrder = parse("recvOrder", `
+	{{/*  Send n, receive it one way or another into x, check that they match. */}}
+	{{/*  Check order of operations along the way by calling functions that check */}}
+	{{/*  that the argument sequence is strictly increasing. */}}
+	order = 0
+	c <- n
+	{{if .Maybe}}
+	{{/*  Outside of select, left-to-right rule applies. */}}
+	{{/*  (Inside select, assignment waits until case is chosen, */}}
+	{{/*  so right hand side happens before anything on left hand side. */}}
+	*fp(&x, 1) = <-fc(c, 2)
+	{{else}}{{if .Maybe}}
+	m[fn(13, 1)] = <-fc(c, 2)
+	x = m[13]
+	{{else}}
+	select {
+	{{/*  Blocking or non-blocking, before the receive. */}}
+	{{/*  The compiler implements two-case select where one is default with custom code, */}}
+	{{/*  so test the default branch both before and after the send. */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Receive from c.  Different cases are direct, indirect, :=, interface, and map assignment. */}}
+	{{if .Maybe}}
+	case *fp(&x, 100) = <-fc(c, 1):
+	{{else}}{{if .Maybe}}
+	case y := <-fc(c, 1):
+		x = y
+	{{else}}{{if .Maybe}}
+	case i = <-fc(c, 1):
+		x = i.(int)
+	{{else}}
+	case m[fn(13, 100)] = <-fc(c, 1):
+		x = m[13]
+	{{end}}{{end}}{{end}}
+	{{/*  Blocking or non-blocking again, after the receive. */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Dummy send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case fc(dummy, 2) <- fn(1, 3):
+		panic("dummy send")
+	{{end}}
+	{{if .Maybe}}
+	case <-fc(dummy, 4):
+		panic("dummy receive")
+	{{end}}
+	{{/*  Nil channel send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case fc(nilch, 5) <- fn(1, 6):
+		panic("nilch send")
+	{{end}}
+	{{if .Maybe}}
+	case <-fc(nilch, 7):
+		panic("nilch recv")
+	{{end}}
+	}
+	{{end}}{{end}}
+	if x != n {
+		die(x)
+	}
+	n++
+`)
+
+var send = parse("send", `
+	{{/*  Send n one way or another, receive it into x, check that they match. */}}
+	{{if .Maybe}}
+	c <- n
+	{{else}}
+	select {
+	{{/*  Blocking or non-blocking, before the receive (same reason as in recv). */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Send c <- n.  No real special cases here, because no values come back */}}
+	{{/*  from the send operation. */}}
+	case c <- n:
+	{{/*  Blocking or non-blocking. */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Dummy send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case dummy <- 1:
+		panic("dummy send")
+	{{end}}
+	{{if .Maybe}}
+	case <-dummy:
+		panic("dummy receive")
+	{{end}}
+	{{/*  Nil channel send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case nilch <- 1:
+		panic("nilch send")
+	{{end}}
+	{{if .Maybe}}
+	case <-nilch:
+		panic("nilch recv")
+	{{end}}
+	}
+	{{end}}
+	x = <-c
+	if x != n {
+		die(x)
+	}
+	n++
+`)
+
+var sendOrder = parse("sendOrder", `
+	{{/*  Send n one way or another, receive it into x, check that they match. */}}
+	{{/*  Check order of operations along the way by calling functions that check */}}
+	{{/*  that the argument sequence is strictly increasing. */}}
+	order = 0
+	{{if .Maybe}}
+	fc(c, 1) <- fn(n, 2)
+	{{else}}
+	select {
+	{{/*  Blocking or non-blocking, before the receive (same reason as in recv). */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Send c <- n.  No real special cases here, because no values come back */}}
+	{{/*  from the send operation. */}}
+	case fc(c, 1) <- fn(n, 2):
+	{{/*  Blocking or non-blocking. */}}
+	{{if .MaybeDefault}}
+	default:
+		panic("nonblock")
+	{{end}}
+	{{/*  Dummy send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case fc(dummy, 3) <- fn(1, 4):
+		panic("dummy send")
+	{{end}}
+	{{if .Maybe}}
+	case <-fc(dummy, 5):
+		panic("dummy receive")
+	{{end}}
+	{{/*  Nil channel send, receive to keep compiler from optimizing select. */}}
+	{{if .Maybe}}
+	case fc(nilch, 6) <- fn(1, 7):
+		panic("nilch send")
+	{{end}}
+	{{if .Maybe}}
+	case <-fc(nilch, 8):
+		panic("nilch recv")
+	{{end}}
+	}
+	{{end}}
+	x = <-c
+	if x != n {
+		die(x)
+	}
+	n++
+`)
+
+var nonblock = parse("nonblock", `
+	x = n
+	{{/*  Test various combinations of non-blocking operations. */}}
+	{{/*  Receive assignments must not edit or even attempt to compute the address of the lhs. */}}
+	select {
+	{{if .MaybeDefault}}
+	default:
+	{{end}}
+	{{if .Maybe}}
+	case dummy <- 1:
+		panic("dummy <- 1")
+	{{end}}
+	{{if .Maybe}}
+	case nilch <- 1:
+		panic("nilch <- 1")
+	{{end}}
+	{{if .Maybe}}
+	case <-dummy:
+		panic("<-dummy")
+	{{end}}
+	{{if .Maybe}}
+	case x = <-dummy:
+		panic("<-dummy x")
+	{{end}}
+	{{if .Maybe}}
+	case **(**int)(nil) = <-dummy:
+		panic("<-dummy (and didn't crash saving result!)")
+	{{end}}
+	{{if .Maybe}}
+	case <-nilch:
+		panic("<-nilch")
+	{{end}}
+	{{if .Maybe}}
+	case x = <-nilch:
+		panic("<-nilch x")
+	{{end}}
+	{{if .Maybe}}
+	case **(**int)(nil) = <-nilch:
+		panic("<-nilch (and didn't crash saving result!)")
+	{{end}}
+	{{if .MustDefault}}
+	default:
+	{{end}}
+	}
+	if x != n {
+		die(x)
+	}
+	n++
+`)
+
+// Code for enumerating all possible paths through
+// some logic.  The logic should call choose(n) when
+// it wants to choose between n possibilities.
+// On successive runs through the logic, choose(n)
+// will return 0, 1, ..., n-1.  The helper maybe() is
+// similar but returns true and then false.
+//
+// Given a function gen that generates an output
+// using choose and maybe, code can generate all
+// possible outputs using
+//
+//	for next() {
+//		gen()
+//	}
+
+type choice struct {
+	i, n int
+}
+
+var choices []choice
+var cp int = -1
+
+func maybe() bool {
+	return choose(2) == 0
+}
+
+func choose(n int) int {
+	if cp >= len(choices) {
+		// never asked this before: start with 0.
+		choices = append(choices, choice{0, n})
+		cp = len(choices)
+		return 0
+	}
+	// otherwise give recorded answer
+	if n != choices[cp].n {
+		panic("inconsistent choices")
+	}
+	i := choices[cp].i
+	cp++
+	return i
+}
+
+func next() bool {
+	if cp < 0 {
+		// start a new round
+		cp = 0
+		return true
+	}
+
+	// increment last choice sequence
+	cp = len(choices) - 1
+	for cp >= 0 && choices[cp].i == choices[cp].n-1 {
+		cp--
+	}
+	if cp < 0 {
+		choices = choices[:0]
+		return false
+	}
+	choices[cp].i++
+	choices = choices[:cp+1]
+	cp = 0
+	return true
+}
diff --git a/test/chan/select6.go b/test/chan/select6.go
new file mode 100644
index 0000000..6e8129f
--- /dev/null
+++ b/test/chan/select6.go
@@ -0,0 +1,34 @@
+// run
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test for select: Issue 2075
+// A bug in select corrupts channel queues of failed cases
+// if there are multiple waiters on those channels and the
+// select is the last in the queue. If further waits are made
+// on the channel without draining it first then those waiters
+// will never wake up. In the code below c1 is such a channel.
+
+package main
+
+func main() {
+	c1 := make(chan bool)
+	c2 := make(chan bool)
+	c3 := make(chan bool)
+	go func() { <-c1 }()
+	go func() {
+		select {
+		case <-c1:
+			panic("dummy")
+		case <-c2:
+			c3 <- true
+		}
+		<-c1
+	}()
+	go func() { c2 <- true }()
+	<-c3
+	c1 <- true
+	c1 <- true
+}
diff --git a/test/chan/select7.go b/test/chan/select7.go
new file mode 100644
index 0000000..f7222ca
--- /dev/null
+++ b/test/chan/select7.go
@@ -0,0 +1,68 @@
+// run
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test select when discarding a value.
+
+package main
+
+import "runtime"
+
+func recv1(c <-chan int) {
+	<-c
+}
+
+func recv2(c <-chan int) {
+	select {
+	case <-c:
+	}
+}
+
+func recv3(c <-chan int) {
+	c2 := make(chan int)
+	select {
+	case <-c:
+	case <-c2:
+	}
+}
+
+func send1(recv func(<-chan int)) {
+	c := make(chan int)
+	go recv(c)
+	runtime.Gosched()
+	c <- 1
+}
+
+func send2(recv func(<-chan int)) {
+	c := make(chan int)
+	go recv(c)
+	runtime.Gosched()
+	select {
+	case c <- 1:
+	}
+}
+
+func send3(recv func(<-chan int)) {
+	c := make(chan int)
+	go recv(c)
+	runtime.Gosched()
+	c2 := make(chan int)
+	select {
+	case c <- 1:
+	case c2 <- 1:
+	}
+}
+
+func main() {
+	send1(recv1)
+	send2(recv1)
+	send3(recv1)
+	send1(recv2)
+	send2(recv2)
+	send3(recv2)
+	send1(recv3)
+	send2(recv3)
+	send3(recv3)
+}
diff --git a/test/chan/select8.go b/test/chan/select8.go
new file mode 100644
index 0000000..20bca3a
--- /dev/null
+++ b/test/chan/select8.go
@@ -0,0 +1,55 @@
+// run
+
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test break statements in a select.
+// Gccgo had a bug in handling this.
+// Test 1,2,3-case selects, so it covers both the general
+// code path and the specialized optimizations for one-
+// and two-case selects.
+
+package main
+
+var ch = make(chan int)
+
+func main() {
+	go func() {
+		for {
+			ch <- 5
+		}
+	}()
+
+	select {
+	case <-ch:
+		break
+		panic("unreachable")
+	}
+
+	select {
+	default:
+		break
+		panic("unreachable")
+	}
+
+	select {
+	case <-ch:
+		break
+		panic("unreachable")
+	default:
+		break
+		panic("unreachable")
+	}
+
+	select {
+	case <-ch:
+		break
+		panic("unreachable")
+	case ch <- 10:
+		panic("unreachable")
+	default:
+		break
+		panic("unreachable")
+	}
+}
diff --git a/test/chan/sendstmt.go b/test/chan/sendstmt.go
new file mode 100644
index 0000000..d296a55
--- /dev/null
+++ b/test/chan/sendstmt.go
@@ -0,0 +1,37 @@
+// run
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test various parsing cases that are a little
+// different now that send is a statement, not an expression.
+
+package main
+
+func main() {
+	chanchan()
+	sendprec()
+}
+
+func chanchan() {
+	cc := make(chan chan int, 1)
+	c := make(chan int, 1)
+	cc <- c
+	select {
+	case <-cc <- 2:
+	default:
+		panic("nonblock")
+	}
+	if <-c != 2 {
+		panic("bad receive")
+	}
+}
+
+func sendprec() {
+	c := make(chan bool, 1)
+	c <- false || true // not a syntax error: same as c <- (false || true)
+	if !<-c {
+		panic("sent false")
+	}
+}
diff --git a/test/chan/sieve1.go b/test/chan/sieve1.go
new file mode 100644
index 0000000..acc310f
--- /dev/null
+++ b/test/chan/sieve1.go
@@ -0,0 +1,56 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test concurrency primitives: classical inefficient concurrent prime sieve.
+
+// Generate primes up to 100 using channels, checking the results.
+// This sieve consists of a linear chain of divisibility filters,
+// equivalent to trial-dividing each n by all primes p ≤ n.
+
+package main
+
+// Send the sequence 2, 3, 4, ... to channel 'ch'.
+func Generate(ch chan<- int) {
+	for i := 2; ; i++ {
+		ch <- i // Send 'i' to channel 'ch'.
+	}
+}
+
+// Copy the values from channel 'in' to channel 'out',
+// removing those divisible by 'prime'.
+func Filter(in <-chan int, out chan<- int, prime int) {
+	for i := range in { // Loop over values received from 'in'.
+		if i%prime != 0 {
+			out <- i // Send 'i' to channel 'out'.
+		}
+	}
+}
+
+// The prime sieve: Daisy-chain Filter processes together.
+func Sieve(primes chan<- int) {
+	ch := make(chan int) // Create a new channel.
+	go Generate(ch)      // Start Generate() as a subprocess.
+	for {
+		// Note that ch is different on each iteration.
+		prime := <-ch
+		primes <- prime
+		ch1 := make(chan int)
+		go Filter(ch, ch1, prime)
+		ch = ch1
+	}
+}
+
+func main() {
+	primes := make(chan int)
+	go Sieve(primes)
+	a := []int{2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97}
+	for i := 0; i < len(a); i++ {
+		if x := <-primes; x != a[i] {
+			println(x, " != ", a[i])
+			panic("fail")
+		}
+	}
+}
diff --git a/test/chan/sieve2.go b/test/chan/sieve2.go
new file mode 100644
index 0000000..09e5c52
--- /dev/null
+++ b/test/chan/sieve2.go
@@ -0,0 +1,188 @@
+// run
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test concurrency primitives: prime sieve of Eratosthenes.
+
+// Generate primes up to 100 using channels, checking the results.
+// This sieve is Eratosthenesque and only considers odd candidates.
+// See discussion at <http://blog.onideas.ws/eratosthenes.go>.
+
+package main
+
+import (
+	"container/heap"
+	"container/ring"
+)
+
+// Return a chan of odd numbers, starting from 5.
+func odds() chan int {
+	out := make(chan int, 50)
+	go func() {
+		n := 5
+		for {
+			out <- n
+			n += 2
+		}
+	}()
+	return out
+}
+
+// Return a chan of odd multiples of the prime number p, starting from p*p.
+func multiples(p int) chan int {
+	out := make(chan int, 10)
+	go func() {
+		n := p * p
+		for {
+			out <- n
+			n += 2 * p
+		}
+	}()
+	return out
+}
+
+type PeekCh struct {
+	head int
+	ch   chan int
+}
+
+// Heap of PeekCh, sorting by head values, satisfies Heap interface.
+type PeekChHeap []*PeekCh
+
+func (h *PeekChHeap) Less(i, j int) bool {
+	return (*h)[i].head < (*h)[j].head
+}
+
+func (h *PeekChHeap) Swap(i, j int) {
+	(*h)[i], (*h)[j] = (*h)[j], (*h)[i]
+}
+
+func (h *PeekChHeap) Len() int {
+	return len(*h)
+}
+
+func (h *PeekChHeap) Pop() (v interface{}) {
+	*h, v = (*h)[:h.Len()-1], (*h)[h.Len()-1]
+	return
+}
+
+func (h *PeekChHeap) Push(v interface{}) {
+	*h = append(*h, v.(*PeekCh))
+}
+
+// Return a channel to serve as a sending proxy to 'out'.
+// Use a goroutine to receive values from 'out' and store them
+// in an expanding buffer, so that sending to 'out' never blocks.
+func sendproxy(out chan<- int) chan<- int {
+	proxy := make(chan int, 10)
+	go func() {
+		n := 16 // the allocated size of the circular queue
+		first := ring.New(n)
+		last := first
+		var c chan<- int
+		var e int
+		for {
+			c = out
+			if first == last {
+				// buffer empty: disable output
+				c = nil
+			} else {
+				e = first.Value.(int)
+			}
+			select {
+			case e = <-proxy:
+				last.Value = e
+				if last.Next() == first {
+					// buffer full: expand it
+					last.Link(ring.New(n))
+					n *= 2
+				}
+				last = last.Next()
+			case c <- e:
+				first = first.Next()
+			}
+		}
+	}()
+	return proxy
+}
+
+// Return a chan int of primes.
+func Sieve() chan int {
+	// The output values.
+	out := make(chan int, 10)
+	out <- 2
+	out <- 3
+
+	// The channel of all composites to be eliminated in increasing order.
+	composites := make(chan int, 50)
+
+	// The feedback loop.
+	primes := make(chan int, 10)
+	primes <- 3
+
+	// Merge channels of multiples of 'primes' into 'composites'.
+	go func() {
+		var h PeekChHeap
+		min := 15
+		for {
+			m := multiples(<-primes)
+			head := <-m
+			for min < head {
+				composites <- min
+				minchan := heap.Pop(&h).(*PeekCh)
+				min = minchan.head
+				minchan.head = <-minchan.ch
+				heap.Push(&h, minchan)
+			}
+			for min == head {
+				minchan := heap.Pop(&h).(*PeekCh)
+				min = minchan.head
+				minchan.head = <-minchan.ch
+				heap.Push(&h, minchan)
+			}
+			composites <- head
+			heap.Push(&h, &PeekCh{<-m, m})
+		}
+	}()
+
+	// Sieve out 'composites' from 'candidates'.
+	go func() {
+		// In order to generate the nth prime we only need multiples of
+		// primes ≤ sqrt(nth prime).  Thus, the merging goroutine will
+		// receive from 'primes' much slower than this goroutine
+		// will send to it, making the buffer accumulate and block this
+		// goroutine from sending, causing a deadlock.  The solution is to
+		// use a proxy goroutine to do automatic buffering.
+		primes := sendproxy(primes)
+
+		candidates := odds()
+		p := <-candidates
+
+		for {
+			c := <-composites
+			for p < c {
+				primes <- p
+				out <- p
+				p = <-candidates
+			}
+			if p == c {
+				p = <-candidates
+			}
+		}
+	}()
+
+	return out
+}
+
+func main() {
+	primes := Sieve()
+	a := []int{2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97}
+	for i := 0; i < len(a); i++ {
+		if x := <-primes; x != a[i] {
+			println(x, " != ", a[i])
+			panic("fail")
+		}
+	}
+}
diff --git a/test/chan/zerosize.go b/test/chan/zerosize.go
new file mode 100644
index 0000000..50aca85
--- /dev/null
+++ b/test/chan/zerosize.go
@@ -0,0 +1,16 @@
+// run
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test making channels of a zero-sized type.
+
+package main
+
+func main() {
+	_ = make(chan [0]byte)
+	_ = make(chan [0]byte, 1)
+	_ = make(chan struct{})
+	_ = make(chan struct{}, 1)
+}