配列遊び

import std.c.stdio;

void main(){
    int[] a;
    a.length = 10;
    for (int i = 1; i < 10; i++){
        a[i] = i;
    }

    int power_of_two(int i){
        return i * i;
    }

    bool power_of_three(int i){
        return ((i % 3) == 0);
    }

    int delegate(int) dg_a = &power_of_two;
    bool delegate(int) dg_b = &power_of_three;

    a = a.each(dg_a);
    a = a.delete_if(dg_b);
    a = a.compact();
    foreach (int i, int x; a){
        printf("%d %d\n", i, x);
    }
}

template each(T){
    T[] each(T[] ary, T delegate(T) dg){
        T[] rary;
        rary.length = ary.length;
        foreach (int i, T t; ary){
            rary[i] = dg(t);
        }
        return rary;
    }
}

template delete_if(T){
    T[] delete_if(T[] ary, bool delegate(T) dg){
        T[] rary;
        rary.length = ary.length;
        foreach (int i, T t; ary){
            if (!dg(t)){
                rary[i] = t;
            }
        }
        return rary;
    }
}

template compact(T){
    T[] compact(T[] ary){
        T[] rary;
        rary.length = ary.length;
        int cnt = 0;
        foreach (T t; ary){
            if (t != T.init){
                rary[cnt] = t;
                cnt++;
            }
        }
        rary.length = cnt;
        return rary;
    }
}

0 1
1 4
2 16
3 25
4 49
5 64

まあよく考えなくてもこんなのわざわざtemplateにせずとも自分で書けばいいしな…とか思った奴は正座。いますぐだ。