• John Carter (51/51) Dec 22 2013 Thanks for all your help understanding the algorithm chaining problem...
• bearophile (8/13) Dec 22 2013 Some functions can't be pure. Some functions can be pure but in
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (4/6) Dec 22 2013 Third option: It compiles and runs OK if you upgrade your compiler. ;)
• John Carter (34/40) Dec 22 2013 Yup.

John Carter <john.carter taitradio.com> writes:

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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"bearophile" <bearophileHUGS lycos.com> writes:

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

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

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 <john.carter taitradio.com> writes:

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 =C3=87ehreli <acehreli yahoo.com> wrot=
e:

 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


--=20
John Carter
Phone : (64)(3) 358 6639
Tait Electronics
PO Box 1645 Christchurch
New Zealand

--=20

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