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-rw-r--r--test/fixedbugs/issue7740.go35
1 files changed, 35 insertions, 0 deletions
diff --git a/test/fixedbugs/issue7740.go b/test/fixedbugs/issue7740.go
new file mode 100644
index 0000000..6bc6249
--- /dev/null
+++ b/test/fixedbugs/issue7740.go
@@ -0,0 +1,35 @@
+// run
+
+// Copyright 2015 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.
+
+// This test computes the precision of the compiler's internal multiprecision floats.
+
+package main
+
+import (
+ "fmt"
+ "math"
+ "runtime"
+)
+
+const ulp = (1.0 + (2.0 / 3.0)) - (5.0 / 3.0)
+
+func main() {
+ // adjust precision depending on compiler
+ var prec float64
+ switch runtime.Compiler {
+ case "gc":
+ prec = math.Inf(1) // exact precision using rational arithmetic
+ case "gccgo":
+ prec = 256
+ default:
+ // unknown compiler
+ return
+ }
+ p := 1 - math.Log(math.Abs(ulp))/math.Log(2)
+ if math.Abs(p-prec) > 1e-10 {
+ fmt.Printf("BUG: got %g; want %g\n", p, prec)
+ }
+}