pure vs std.range.retro

2013-12-22 Thread John Carter 
Thanks for all your help understanding the algorithm chaining problem...

Now I have another gotcha.

This code compiles and runs OK if I remove the keyword pure or if I
remove the .retro

As I understand it retro should affect the pureness of the the function.

If I put the keyword in, it fails to instantiate the template...
import std.algorithm;
import std.array;
import std.stdio;
import std.range;

pure auto huh( in uint[] digitArray, in uint value)
{
   return find!( (a,b) = (a  b))( digitArray.retro, value);
}

unittest {
   auto test = [11u, 1u, 1u, 10u];
   auto s = huh( test, 10u);
   writeln( s);
}

dmd -unittest -main  doesnt_work.d  ./doesnt_work
/usr/include/dmd/phobos/std/algorithm.d(3508): Error: pure function
'doesnt_work.huh' cannot call impure function
'std.range.retro!(const(uint)[]).retro.Result.popFront'
/usr/include/dmd/phobos/std/algorithm.d(3510): Error: pure function
'doesnt_work.huh' cannot call impure function
'std.range.retro!(const(uint)[]).retro.Result.front'
doesnt_work.d(8): Error: template instance doesnt_work.huh.find!(__lambda3,
Result, const(uint)) error instantiating

-- 
John Carter
Phone : (64)(3) 358 6639
Tait Electronics
PO Box 1645 Christchurch
New Zealand

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Re: pure vs std.range.retro

2013-12-22 Thread bearophile 

John Carter:

Thanks for all your help understanding the algorithm chaining 
problem...


Now I have another gotcha.

This code compiles and runs OK if I remove the keyword pure 
or if I remove the .retro


Some functions can't be pure. Some functions can be pure but in 
Phobos are not yet pure, often because they call other basic 
functions that are not yet pure. And probably some functions are 
not yet pure because of some compiler bug/limits. To know what is 
your case you have to take a look at the Phobos code.


Bye,
bearophile

Re: pure vs std.range.retro

2013-12-22 Thread Ali Çehreli 

On 12/22/2013 02:37 PM, John Carter wrote:

 This code compiles and runs OK if I remove the keyword pure or if I
 remove the .retro

Third option: It compiles and runs OK if you upgrade your compiler. ;)

Works with DMD64 D Compiler v2.065-devel-41ebb59.

Ali

Re: pure vs std.range.retro

2013-12-22 Thread John Carter 
Yup.

That's the answer.

Upgraded to 2.064 and good things happened.

Diff shows flocks of diffs in std.range

Thanks.


On Mon, Dec 23, 2013 at 1:21 PM, Ali Çehreli acehr...@yahoo.com wrote:

 On 12/22/2013 02:37 PM, John Carter wrote:

  This code compiles and runs OK if I remove the keyword pure or if I
  remove the .retro

 Third option: It compiles and runs OK if you upgrade your compiler. ;)

 Works with DMD64 D Compiler v2.065-devel-41ebb59.

 Ali




-- 
John Carter
Phone : (64)(3) 358 6639
Tait Electronics
PO Box 1645 Christchurch
New Zealand

-- 

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This email, including any attachments, is only for the intended recipient. 
It is subject to copyright, is confidential and may be the subject of legal 
or other privilege, none of which is waived or lost by reason of this 
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distribute or reproduce such email, any attachments, or any part thereof. 
If you have received a message in error, please notify the sender 
immediately and erase all copies of the message and any attachments.
Unfortunately, we cannot warrant that the email has not been altered or 
corrupted during transmission nor can we guarantee that any email or any 
attachments are free from computer viruses or other conditions which may 
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recipient relies upon its own procedures and assumes all risk of use and of 
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