Re: Function template advice

[Ali Çehreli via Digitalmars-d-learn]

On 01/18/2017 02:02 PM, Jordan Wilson wrote:

I have a simple comparison function:

struct Foo {
    string bar;
}

auto sameGroup(T,S) (T a, S b) {
    static assert (is(T == string) || is(T == Foo));
    static assert (is(S == string) || is(S == Foo));

    string aStr;
    string bStr;
    static if (is(T == string)){
        aStr = a;
    } else {
        aStr = a.bar;
    }
    static if (is(S == string)){
        bStr = b;
    } else {
        bStr = b.bar;
    }
    return equal (aStr,bStr);
}

This works, but just wondered if there was an easier way?

Is there a way to do "static if" in shorthand, like:
auto aStr = (static if (is(T==string)) ? a : a.bar

Yes, can be better with something similar to the following:

struct Foo {
    string bar;
}

string value(U : Foo)(U u) {
    return u.bar;
}

string value(U : string)(U u) {
    return u;
}

auto sameGroup(T,S) (T a, S b) {
    static assert (is(T == string) || is(T == Foo));
    static assert (is(S == string) || is(S == Foo));

    import std.algorithm;
    return equal (value(a), value(b));
}

void main() {
    assert(sameGroup("a", "b") == false);
    assert(sameGroup("a", Foo("a")) == true);
    assert(sameGroup(Foo("x"), "b") == false);
    assert(sameGroup(Foo("z"), Foo("z")) == true);
}

Ali