Hello. I not found realization of pure format function (in phobos it not pure) and write minimal custom realization.
https://github.com/dexset/desstdx/blob/master/source/des/stdx/pformat.d#L472
Now it works with numbers and strings, but in future I improve it.
Maybe my realization can help someone =)
Contained in the dub package http://code.dlang.org/packages/desstdx

If pure format exists tell about it, please.

On Thursday, 4 June 2015 at 14:33:39 UTC, Oleg B wrote:
> Hello. I not found realization of pure format function (in phobos it not pure) and write minimal custom realization.
> https://github.com/dexset/desstdx/blob/master/source/des/stdx/pformat.d#L472
> Now it works with numbers and strings, but in future I improve it.
> Maybe my realization can help someone =)
> Contained in the dub package http://code.dlang.org/packages/desstdx
>
> If pure format exists tell about it, please.

std.format.format should be pure if its arguments have pure toString methods or are built-in types. There may be implementation issues preventing it for one reason or another (I don't know), but if so, then that's a bug that needs to be fixed. Regardless, there should be no need for a separate format function which is pure.

- Jonathan M Davis

On Thursday, 4 June 2015 at 16:21:54 UTC, Jonathan M Davis wrote:
> On Thursday, 4 June 2015 at 14:33:39 UTC, Oleg B wrote:
>> Hello. I not found realization of pure format function (in phobos it not pure) and write minimal custom realization.
>> https://github.com/dexset/desstdx/blob/master/source/des/stdx/pformat.d#L472
>> Now it works with numbers and strings, but in future I improve it.
>> Maybe my realization can help someone =)
>> Contained in the dub package http://code.dlang.org/packages/desstdx
>>
>> If pure format exists tell about it, please.
>
> std.format.format should be pure if its arguments have pure toString methods or are built-in types. There may be implementation issues preventing it for one reason or another (I don't know), but if so, then that's a bug that needs to be fixed. Regardless, there should be no need for a separate format function which is pure.
>
> - Jonathan M Davis

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...

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.

Ali

On Thursday, 4 June 2015 at 18:08:09 UTC, Ali Çehreli wrote:
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.
>
> Ali

That is not it (if it is, it's a bug), as D allows pure functions to set and check those flags.
http://dlang.org/function.html#pure-functions

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

On Thursday, 4 June 2015 at 18:27:16 UTC, Steven Schveighoffer wrote:
> On 6/4/15 2:08 PM, Ali Çehreli wrote:
>> [...]
>
> 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

Is it possible to get this fixed in mainline phobos? Not having a pure format() is really annoying.

On Thursday, 4 June 2015 at 17:02:46 UTC, Oleg B wrote:
> On Thursday, 4 June 2015 at 16:21:54 UTC, Jonathan M Davis wrote:
>
> I think toString for float must be pure, but in practice it's not.
>
>
> 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...

And I also remember that format doesn't work in CT, so it was really uncomfortable that a can't initialize array of special values for algorithm in CT. It was a more than year ago, possible something changes.

On Thursday, 2 July 2015 at 04:41:51 UTC, HaraldZealot wrote:
> On Thursday, 4 June 2015 at 17:02:46 UTC, Oleg B wrote:
>> On Thursday, 4 June 2015 at 16:21:54 UTC, Jonathan M Davis wrote:
>>
>> I think toString for float must be pure, but in practice it's not.
>>
>>
>> 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...
>
> And I also remember that format doesn't work in CT, so it was really uncomfortable that a can't initialize array of special values for algorithm in CT. It was a more than year ago, possible something changes.

pretty sure std.metastring(s?) was deprecated 'cos format works at CT

On 02-Jul-2015 12:53, Nicholas Wilson wrote:
> On Thursday, 2 July 2015 at 04:41:51 UTC, HaraldZealot wrote:
>> On Thursday, 4 June 2015 at 17:02:46 UTC, Oleg B wrote:
>>> On Thursday, 4 June 2015 at 16:21:54 UTC, Jonathan M Davis wrote:
>>>
>>> I think toString for float must be pure, but in practice it's not.
>>>
>>>
>>> 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...
>>
>> And I also remember that format doesn't work in CT, so it was really
>> uncomfortable that a can't initialize array of special values for
>> algorithm in CT. It was a more than year ago, possible something changes.
>
> pretty sure std.metastring(s?) was deprecated 'cos format works at CT

Yeah, formattedWrite definitely works  at CTFE these days.

-- 
Dmitry Olshansky