Voldemort types article

eponymous.d

module eponymous;

template inputChain(R1, R2)
    if(isInputRange!R1 && isInputRange!R2 &&
       is(ElementType!R1 == ElementType!R2))
{
    auto inputChain(R1 r1, R2 r2)
    {
        ...
    }
}

simplechain.d

import std.range;

auto inputChain(R1, R2)(R1 r1, R2 r2)
    if(isInputRange!R1 && isInputRange!R2 &&
       is(ElementType!R1 == ElementType!R2))
{
    static struct Chain
    {
        R1 r1;
        R2 r2;
        
        auto front() { return r1.empty ? r2.front : r1.front; }
        void popFront()
        {
            if(r1.empty)
                r2.popFront;
            else
                r1.popFront;
        }
        bool empty() { return r1.empty && r2.empty; }
    }

    return Chain(r1, r2);
}

simplechain2.d

module simplechain;
import std.range;

auto inputChain(R1, R2)(R1 r1, R2 r2)
    if(isInputRange!R1 && isInputRange!R2 &&
       is(ElementType!R1 == ElementType!R2))
{
    static struct Chain
    {
        R1 r1;
        R2 r2;
        
        auto front() { throw new Exception(""); return r1.empty ? r2.front : r1.front; }
        void popFront()
        {
            if(r1.empty)
                r2.popFront;
            else
                r1.popFront;
        }
        bool empty() { return r1.empty && r2.empty; }
    }

    return Chain(r1, r2);
}

simplechain3.d

module simplechain;
import std.range;

private struct Chain(R1, R2)
    if(isInputRange!R1 && isInputRange!R2 &&
       is(ElementType!R1 == ElementType!R2))
{
    R1 r1;
    R2 r2;

    auto front() { throw new Exception(""); return r1.empty ? r2.front : r1.front; }
    void popFront()
    {
        if(r1.empty)
            r2.popFront;
        else
            r1.popFront;
    }
    bool empty() { return r1.empty && r2.empty; }
}

auto inputChain(R1, R2)(R1 r1, R2 r2)
    if(isInputRange!R1 && isInputRange!R2 &&
       is(ElementType!R1 == ElementType!R2))
{
    return Chain!(R1, R2)(r1, r2); // note the explicit instantation
}

simplechain4.d

module simplechain;
import std.range;

template inputChain(R1, R2)
    if(isInputRange!R1 && isInputRange!R2 &&
       is(ElementType!R1 == ElementType!R2))
{
    struct Chain
    {
        R1 r1;
        R2 r2;

        auto front() { throw new Exception(""); return r1.empty ? r2.front : r1.front; }
        void popFront()
        {
            if(r1.empty)
                r2.popFront;
            else
                r1.popFront;
        }
        bool empty() { return r1.empty && r2.empty; }
    }

    auto inputChain(R1 r1, R2 r2)
    {
        return Chain(r1, r2);
    }
}

simplechainexception.d

...
        auto front() { throw new Exception(""); return r1.empty? ... }
...

testchain.d

import simplechain;
import std.stdio;

void main()
{
    auto ch = inputChain("hello, ", "world!");
    writeln(ch);
}

testchain2.d

import simplechain;
import std.stdio;

void main()
{
    auto ch = inputChain("hello ", "there, ").inputChain("world!");
    writeln(ch);
}