ifとmatchで階乗を書いて、実行時間を比べてみる。

factorial.rs

extern crate time;

fn factorial(n: uint) -> uint {
    if n > 1 {
        n * factorial(n - 1)
    } else {
        n
    }
}

fn factorial_match(n: uint) -> uint {
    match n {
        0 | 1 => n,
        _ => n * factorial(n - 1)
    }
}

fn main() {
    loop {
        let if_start = time::get_time();
        for _ in range(0, 10000u) {
            for _ in range(0, 1000u) {
                let _ = factorial(10);
            }
        }
        let if_end = time::get_time();
        println!("if {}", if_end - if_start);

        let match_start = time::get_time();
        for _ in range(0, 10000u) {
            for _ in range(0, 1000u) {
                let _ = factorial_match(10);
            }
        }
        let match_end = time::get_time();
        println!("match {}", match_end - match_start);
    }
}

ああああ・・・
完全に間違ってました