Cute 'findBest' with iter and fold and without evil copies.

gistfile1.rs

use std::num::*;

// Given a collection and a score function, find the item with highest score.
fn findBest<'t,T,C:Ord>(src:&'t [T], scoreFunc:&fn(x:&'t T)->C)->Option<(&'t T,uint,C)> {
    let mut it = src.iter();
    let mut i = 0;
    match it.next() {
        None => None,
        Some(first) => {
            let firstScore = scoreFunc(first);
            let firstResult = (first,0,firstScore);
            Some(do it.fold(firstResult) |old,cur| {
                i = i + 1;
                let &(_,_,oldScore) = &old;
                let newScore = scoreFunc(cur);
                if (newScore > oldScore) {
                    (cur,i,newScore)
                } else {
                    old
                }
            })
        }
    }
}

fn main() {
        let array=~[1i,4i,3i,10i,-15i];
        println(match do findBest(array) |x|{-abs(x-5i)} {
                Some((item,_,_)) => fmt!("Closest to 5: =%d ",*item),
                None => ~"no inputs"
        })
}