dmd 2.029 release

[bearophile]

Don:
> Actually it's not so difficult. I've created a patch for bug 2807 -- 
> it's only 5 lines long! It gives an error message if a nested pure 
> function accesses a mutable variable from an outer scope.

Thank you very much Don, your work helps a lot.

Every time I try a tiny program I find something I don't understand:

import std.stdio: writeln;
import std.math: sqrt;
import std.conv: to;

void main(string[] args) {
    double x = args.length == 2 ? to!(double)(args[1]) : 4.0;
    writeln(sqrt(x) + sqrt(x));
}

I have also tried with std.math.sin with similar results:

L0:		enter	8,0
		mov	EAX,8[EBP]
		cmp	EAX,2
		jne	L30
		cmp	EAX,1
		ja	L1B
		mov	EAX,6
		call	near ptr _D6test7__arrayZ
L1B:		mov	EDX,0Ch[EBP]
		mov	EAX,8[EBP]
		mov	EAX,8[EDX]
		mov	EDX,0Ch[EDX]
		push	EDX
		push	EAX
		call	near ptr _D3std4conv13__T2toTdTAyaZ2toFAyaZd
		jmp short	L36
L30:		fld	qword ptr FLAT:_DATA[00h]
L36:		fstp	qword ptr -8[EBP]
		fld	qword ptr -8[EBP]
		fsin
		fld	qword ptr -8[EBP]
		fsin
		faddp	ST(1),ST
		sub	ESP,0Ch
		fstp	tbyte ptr [ESP]
		call	near ptr _D3std5stdio14__T7writelnTeZ7writelnFeZv
		xor	EAX,EAX
		leave
		ret

Isn't sin(x)+sin(x) pure? Even if the compiler doesn't want to replace x+x with x*2 because x is a floating point, it can do:

y = sin(x)
y+y

And that gives the same result even with FPs.

Note: with SSE2 it's even possible to perform two sqrt(double) at the same time, so a compiler can implement sin(x)+sin(y) with a single instruction (SQRTSD) (plus eventually some register loading/unloading).

Bye,
bearophile