Function that calculates in compile time when it can

[Minas Mina]

On Monday, 6 August 2012 at 15:56:52 UTC, Namespace wrote:
> Take a look into std.math:
> https://github.com/D-Programming-Language/phobos/blob/master/std/math.d

I found this:

real sin(real x) @safe pure nothrow; /* intrinsic */

And these:

creal sin(creal z) @safe pure nothrow
{
      creal cs = expi(z.re);
      creal csh = coshisinh(z.im);
      return cs.im * csh.re + cs.re * csh.im * 1i;
}

/** ditto */
ireal sin(ireal y) @safe pure nothrow
{
      return cosh(y.im)*1i;
}

I don't see anything about ctfe. Maybe I didn't understand well
and sin is not evaluated at compile time. Can someone clarify
this?