| // Copyright 2014 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| |
| #![feature(advanced_slice_patterns)] |
| #![feature(slice_patterns)] |
| |
| fn foldl<T, U, F>(values: &[T], |
| initial: U, |
| mut function: F) |
| -> U where |
| U: Clone, |
| F: FnMut(U, &T) -> U, |
| { |
| match values { |
| [ref head, tail..] => |
| foldl(tail, function(initial, head), function), |
| [] => initial.clone() |
| } |
| } |
| |
| fn foldr<T, U, F>(values: &[T], |
| initial: U, |
| mut function: F) |
| -> U where |
| U: Clone, |
| F: FnMut(&T, U) -> U, |
| { |
| match values { |
| [head.., ref tail] => |
| foldr(head, function(tail, initial), function), |
| [] => initial.clone() |
| } |
| } |
| |
| pub fn main() { |
| let x = &[1, 2, 3, 4, 5]; |
| |
| let product = foldl(x, 1, |a, b| a * *b); |
| assert_eq!(product, 120); |
| |
| let sum = foldr(x, 0, |a, b| *a + b); |
| assert_eq!(sum, 15); |
| } |