import std.stdio;
import std.math;

//template eltype(X:X[]) { alias X eltype; } // use typeof(X.init[0]) instead

// A declaration of X
template declare(X) { X declare; }

// The return type of a function type FunTy taking 1 argument of type ArgTy
template rettype(FunTy,ArgTy) { alias typeof(declare!(FunTy)(ArgTy.init)) rettype; }

template map(ArrTy, FunTy) {
	 rettype!(FunTy,typeof(ArrTy.init[0]))[] map(ArrTy arr, FunTy fun) {
		rettype!(FunTy,typeof(arr[0]))[] ret;
		ret.length = arr.length;
		foreach(uint i, typeof(arr[0]) t; arr)
			ret[i] = fun(t);
		return ret;
	}
}

template filter(ArrTy, FunTy) {
	ArrTy filter(ArrTy arr, FunTy fun) {
		ArrTy ret;
		foreach(typeof(arr[0]) a; arr)
			if (fun(a))
				ret ~= a;
		return ret;
	}
}

void main() {
	const int[] data = [1,2,3,76,2,1,3,45,2];
	writefln("data = ", data);

	auto squared = map(data, function int(int x) { return x*x; });
	writefln("squared = ", squared);
	
	auto sqrooted = map(data, function double(int x) { return sqrt(cast(float)x); });
	writefln("sqrooted = ", sqrooted);

	auto even = filter(data, function bool(int x) { return (x&1) == 0; });
	writefln("even = ", even);

	auto odd = filter(data, function bool(int x) { return (x&1) == 1; });
	writefln("odd = ", odd);
}