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.
// 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 (integer, boolean) = pair; (boolean, integer) } // 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 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!("the 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
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Recap: Add the
fmt::Displaytrait to the Matrixstructin the above example, so that if you switch from printing the debug format{:?}to the display format{}, you see the following output:( 1.1 1.2 ) ( 2.1 2.2 )You may want to refer back to the example for print display.
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Add a
transposefunction using thereversefunction as a template, which accepts a matrix as an argument, and returns a matrix in which two elements have been swapped. For example:println!("Matrix:\n{}", matrix); println!("Transpose:\n{}", transpose(matrix));results in the output:
Matrix: ( 1.1 1.2 ) ( 2.1 2.2 ) Transpose: ( 1.1 2.1 ) ( 1.2 2.2 )