map & filter for AAs

[spir]

Hello,


Is there map & filter for AAs? Is it useful?
Below example,
Denis


struct Pair (K,V) { K k; V v; }

V2[K2] map (K1,V1, K2,V2) (V1[K1] aa1, Pair!(K2,V2) delegate (K1,V1) f) {
     V2[K2] aa2;
     Pair!(K2,V2) pair;
     foreach (k,v ; aa1) {
         pair = f(k,v);
         aa2[pair.k] = pair.v;
     }
     return aa2;
}

V1[K1] filter (K1,V1) (V1[K1] aa1, bool delegate (K1,V1) f) {
     V1[K1] aa2;
     foreach (k,v ; aa1) {
         if (f(k,v))
             aa2[k] = v;
     }
     return aa2;
}

unittest {
     char[uint] aa1 = [65:'a', 66:'b', 67:'c'];

     // map
     Pair!(char,uint) inversed (uint u,char c) { return Pair!(char,uint)(c,u); }
     auto aa2 = map!(uint,char, char,uint)(aa1, &inversed);
     writefln("map inversed  : [%s] --> [%s]", aa1,aa2);

     // filter
     bool odd (uint u,char c) { return (u%2 == 1); }
     auto aa3 = filter!(uint,char)(aa1, &odd);
     writefln("filter odd    : [%s] --> [%s]", aa1,aa3);
     bool c (uint u,char c) { return (c == 'c'); }
     auto aa4 = filter!(uint,char)(aa1, &c);
     writefln("filter c      : [%s] --> [%s]", aa1,aa4);
}
void main() {}

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