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Code

import std.typetuple;
import std.typecons;
import std.stdio;

private template filterWithNum(alias F, int N, T...)
{
    static if (T.length == 0)
        alias TypeTuple!() filterWithNum;
    else
    {   
        static if (F!(N, T[0]))
            alias TypeTuple!(T[0],
                filterWithNum!(F, N+1, T[1 .. $])) filterWithNum;
        else
            alias filterWithNum!(F, N+1, T[1 .. $]) filterWithNum;
    }   
}

template filter(alias F, T...)
{
    static if (T.length == 0)
        alias TypeTuple!() filter;
    else static if (is(typeof(F!(0,T[0]) == true)))
    {   
        alias filterWithNum!(F,0,T) filter;
    }   
    else static if (is(typeof(F!(T[0]))))
    {   
        static if (F!(T[0]))
            alias TypeTuple!(T[0],
                filter!(F, T[1 .. $])) filter;
        else
            alias filter!(F, T[1 .. $]) filter;
    }   
    else
    {   
        static assert(0, "Wrong predicate supplied");
    }   
}

template even( int N, alias T ) 
{
    enum bool even = ! (N % 2); 
}

template even2( alias T ) 
{
    static if (!is(typeof(!(T % 2))))
        enum bool even2 = false;
    else
        enum bool even2 = ! (T % 2); 
}

void main()
{
    alias TypeTuple!( 1, "lalalal", 4, 5, 6 ) args;

writeln(tuple( filter!(even, args) )); 
    writeln(tuple( filter!(even2, args) )); 
}

Application output:

Tuple!(int,int,int)(1, 4, 6)
Tuple!(int,int)(4, 6)

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Author: Guest

Views: 169

Private: no

Expires: Never

Uploaded: 18.06.12 23:35

Votes: 0

Compilation

Compiler: DMD 2.062

Pointer size: m64

Code

Application output:

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