41 lines
837 B
Rust
41 lines
837 B
Rust
use std::fmt::Debug;
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fn foldl<T, U, F>(values: &[T], initial: U, mut function: F) -> U
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where
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U: Clone + Debug,
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T: Debug,
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F: FnMut(U, &T) -> U,
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{
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match values {
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[head, tail @ ..] => foldl(tail, function(initial, head), function),
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[] => {
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let res = initial.clone();
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res
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}
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}
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}
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fn foldr<T, U, F>(values: &[T], initial: U, mut function: F) -> U
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where
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U: Clone,
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F: FnMut(&T, U) -> U,
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{
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match values {
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[head @ .., tail] => foldr(head, function(tail, initial), function),
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[] => {
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let res = initial.clone();
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res
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}
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}
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}
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pub fn main() {
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let x = &[1, 2, 3, 4, 5];
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let product = foldl(x, 1, |a, b| a * *b);
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assert_eq!(product, 120);
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let sum = foldr(x, 0, |a, b| *a + b);
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assert_eq!(sum, 15);
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}
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