Re: UFCS with constructors

[Ali Çehreli]

On 11/06/2013 03:04 AM, bearophile wrote:
import std.typecons: Typedef;
alias Foo = Typedef!double;
void main() {
     auto a1 = Foo(1);
     pragma(msg, typeof(a1));
     auto a2 = 1.Foo;
     pragma(msg, typeof(a2));
     auto a3 = Foo(-1);
     pragma(msg, typeof(a3));
     auto a4 = -1.Foo;
     pragma(msg, typeof(a4));
}

It prints:

Typedef!(double, nan)
Typedef!(double, nan)
Typedef!(double, nan)
double


Is this expected/acceptable/good?

Bye,
bearophile

I would be very surprised if unary "-" produced a different type from 
the operand:

import std.typecons: Typedef;

alias Foo = Typedef!double;

void main() {
    auto a = 1.Foo;
    auto b = -a;
    static assert (is (typeof(a) == typeof(b)));    // FAILS!
}

After all, we are used to hidden bugs based on that expectation: ;)

void main()
{
    uint a = 1;
    auto b = -a;

    assert(b == uint.max);                  // WT?
    static assert(is (typeof(b) == uint));  // <-- the reason
}

Seriously though, yeah, unary "-" must return Typedef!(double, nan).

Ali