1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
|
# Tuples
A tuple is a collection of values of different types. Tuples are constructed
using parentheses `()`, and each tuple itself is a value with type signature
`(T1, T2, ...)`, where `T1`, `T2` are the types of its members. Functions can
use tuples to return multiple values, as tuples can hold any number of values.
```rust,editable
// Tuples can be used as function arguments and as return values.
fn reverse(pair: (i32, bool)) -> (bool, i32) {
// `let` can be used to bind the members of a tuple to variables.
let (int_param, bool_param) = pair;
(bool_param, int_param)
}
// The following struct is for the activity.
#[derive(Debug)]
struct Matrix(f32, f32, f32, f32);
fn main() {
// A tuple with a bunch of different types.
let long_tuple = (1u8, 2u16, 3u32, 4u64,
-1i8, -2i16, -3i32, -4i64,
0.1f32, 0.2f64,
'a', true);
// Values can be extracted from the tuple using tuple indexing.
println!("Long tuple first value: {}", long_tuple.0);
println!("Long tuple second value: {}", long_tuple.1);
// Tuples can be tuple members.
let tuple_of_tuples = ((1u8, 2u16, 2u32), (4u64, -1i8), -2i16);
// Tuples are printable.
println!("tuple of tuples: {:?}", tuple_of_tuples);
// But long Tuples (more than 12 elements) cannot be printed.
//let too_long_tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13);
//println!("Too long tuple: {:?}", too_long_tuple);
// TODO ^ Uncomment the above 2 lines to see the compiler error
let pair = (1, true);
println!("Pair is {:?}", pair);
println!("Uhe reversed pair is {:?}", reverse(pair));
// To create one element tuples, the comma is required to tell them apart
// from a literal surrounded by parentheses.
println!("One element tuple: {:?}", (5u32,));
println!("Just an integer: {:?}", (5u32));
// Tuples can be destructured to create bindings.
let tuple = (1, "hello", 4.5, true);
let (a, b, c, d) = tuple;
println!("{:?}, {:?}, {:?}, {:?}", a, b, c, d);
let matrix = Matrix(1.1, 1.2, 2.1, 2.2);
println!("{:?}", matrix);
}
```
### Activity
1. *Recap*: Add the `fmt::Display` trait to the `Matrix` struct in the above
example, so that if you switch from printing the debug format `{:?}` to the
display format `{}`, you see the following output:
```text
( 1.1 1.2 )
( 2.1 2.2 )
```
You may want to refer back to the example for [print display][print_display].
2. Add a `transpose` function using the `reverse` function as a template, which
accepts a matrix as an argument, and returns a matrix in which two elements
have been swapped. For example:
```rust,ignore
println!("Matrix:\n{}", matrix);
println!("Transpose:\n{}", transpose(matrix));
```
Results in the output:
```text
Matrix:
( 1.1 1.2 )
( 2.1 2.2 )
Transpose:
( 1.1 2.1 )
( 1.2 2.2 )
```
[print_display]: ../hello/print/print_display.md
|
