On 6/4/15 2:08 PM, Ali Çehreli wrote:
On 06/04/2015 10:02 AM, Oleg B wrote:
> I think toString for float must be pure, but in practice it's not.
>
> import std.stdio;
> import std.string;
> string test( float abc ) pure { return format( "abc: % 6.3f", abc ); }
> void main() { writeln( test( 13.3 ) ); }
>
> $ rdmd purefmtfloating.d
> purefmtfloating.d(3): Error: pure function 'purefmtfloating.test' cannot
> call impure function 'std.format.format!(char, float).format'
> Failed: ["dmd", "-v", "-o-", "purefmtfloating.d", "-I."]
>
> DMD64 v2.067.1
>
> It's a bug? I read what std.format.format using libc sprintf
>
http://www.digitalmars.com/d/archives/digitalmars/D/learn/std.conv.to_purity_68957.html
> and if it try it's not a bug...
Floating point operations share global state ("flags" or "attributes")
for rounding mode, exception and trap handling. Perhaps that's why
floating point format cannot be pure.
That is a terrible excuse if that is what the issue is.
I recalled Don discussing this, found these threads (they are old, maybe
something has gotten better since then):
http://forum.dlang.org/post/gpddrm$20u7$1...@digitalmars.com
http://forum.dlang.org/post/h8ad5r$22jj$1...@digitalmars.com
From that, it does seem that D does not care about the rounding modes,
and just considers the code pure.
-Steve
