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);
}
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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:
( 1.1 1.2 )
( 2.1 2.2 )
You may want to refer back to the example for 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:
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 )
An array is a collection of objects of the same type T, stored in contiguous memory. Arrays are created using brackets [], and their length, which is known at compile time, is part of their type signature [T; length].
Slices are similar to arrays, but their length is not known at compile time. Instead, a slice is a two-word object, the first word is a pointer to the data, and the second word is the length of the slice. The word size is the same as usize, determined by the processor architecture eg 64 bits on an x86-64. Slices can be used to borrow a section of an array, and have the type signature &[T].
use std::mem;
// This function borrows a slice
fn analyze_slice(slice: &[i32]) {
println!("first element of the slice: {}", slice[0]);
println!("the slice has {} elements", slice.len());
}
fn main() {
// Fixed-size array (type signature is superfluous)
let xs: [i32; 5] = [1, 2, 3, 4, 5];
// All elements can be initialized to the same value
let ys: [i32; 500] = [0; 500];
// Indexing starts at 0
println!("first element of the array: {}", xs[0]);
println!("second element of the array: {}", xs[1]);
// `len` returns the count of elements in the array
println!("number of elements in array: {}", xs.len());
// Arrays are stack allocated
println!("array occupies {} bytes", mem::size_of_val(&xs));
// Arrays can be automatically borrowed as slices
println!("borrow the whole array as a slice");
analyze_slice(&xs);
// Slices can point to a section of an array
// They are of the form [starting_index..ending_index]
// starting_index is the first position in the slice
// ending_index is one more than the last position in the slice
println!("borrow a section of the array as a slice");
analyze_slice(&ys[1 .. 4]);
// Out of bound indexing causes compile error
println!("{}", xs[5]);
}
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Rust custom data types are formed mainly through the two keywords:
• struct: define a structure
• enum: define an enumeration
Constants can also be created via the const and static keywords.
There are three types of structures ("structs") that can be created using the struct keyword: