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64 lines
1.9 KiB
Rust
64 lines
1.9 KiB
Rust
// ./src/primitives/array.md
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use std::mem;
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// This function borrows a slice
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fn analyze_slice(slice: &[i32]) {
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println!("first element of the slice: {}", slice[0]);
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println!("the slice has {} elements", slice.len());
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}
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fn part0() {
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// Fixed-size array (type signature is superfluous)
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let xs: [i32; 5] = [1, 2, 3, 4, 5];
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// All elements can be initialized to the same value
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let ys: [i32; 500] = [0; 500];
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// Indexing starts at 0
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println!("first element of the array: {}", xs[0]);
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println!("second element of the array: {}", xs[1]);
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// `len` returns the count of elements in the array
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println!("number of elements in array: {}", xs.len());
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// Arrays are stack allocated
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println!("array occupies {} bytes", mem::size_of_val(&xs));
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// Arrays can be automatically borrowed as slices
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println!("borrow the whole array as a slice");
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analyze_slice(&xs);
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// Slices can point to a section of an array
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// They are of the form [starting_index..ending_index]
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// starting_index is the first position in the slice
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// ending_index is one more than the last position in the slice
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println!("borrow a section of the array as a slice");
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analyze_slice(&ys[1 .. 4]);
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// Example of empty slice `&[]`
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let empty_array: [u32; 0] = [];
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assert_eq!(&empty_array, &[]);
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assert_eq!(&empty_array, &[][..]); // same but more verbose
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// Arrays can be safely accessed using `.get`, which returns an
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// `Option`. This can be matched as shown below, or used with
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// `.expect()` if you would like the program to exit with a nice
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// message instead of happily continue.
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for i in 0..xs.len() + 1 { // OOPS, one element too far
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match xs.get(i) {
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Some(xval) => println!("{}: {}", i, xval),
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None => println!("Slow down! {} is too far!", i),
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}
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}
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// Out of bound indexing causes compile error
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//println!("{}", xs[5]);
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}
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pub fn main() {
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part0();
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}
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