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 "pure"ness 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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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

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

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 <acehreli@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

-- 

------------------------------
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
transmission.
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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
damage or interfere with recipient data, hardware or software. The
recipient relies upon its own procedures and assumes all risk of use and of
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------------------------------