• =?UTF-8?B?Tm9yZGzDtnc=?= (7/7) Sep 26 2015 Why is the following code not pure:
• cym13 (4/11) Sep 26 2015 Maybe because of floating point numbers uncertainty that would
• Daniel Murphy (4/19) Sep 27 2015 Probably because it uses C's float formatting functions, and they
• Xinok (10/17) Sep 26 2015 I don't know the exact reason but I found a couple of functions
• Jack Stouffer (5/12) Sep 26 2015 Please make an issue on https://issues.dlang.org and I'll take a
• =?UTF-8?B?Tm9yZGzDtnc=?= (4/8) Sep 28 2015 Already file here:

=?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

Why is the following code not pure:

     float x = 3.14;
     import std.conv : to;
     auto y = x.to!string;


???

Is there a reason for it not being pure? If not, this is a 
serious problem as this is such a fundamental function.

cym13 <cpicard openmailbox.org> writes:

On Saturday, 26 September 2015 at 17:08:00 UTC, Nordlöw wrote:
 Why is the following code not pure:

     float x = 3.14;
     import std.conv : to;
     auto y = x.to!string;


 ???

 Is there a reason for it not being pure? If not, this is a 
 serious problem as this is such a fundamental function.

Maybe because of floating point numbers uncertainty that would 
cause the resulting string to be different for two equivalent 
inputs? I can't seem to put an example together though.

Daniel Murphy <yebbliesnospam gmail.com> writes:

On 27/09/2015 3:14 AM, cym13 wrote:
 On Saturday, 26 September 2015 at 17:08:00 UTC, Nordlöw wrote:
 Why is the following code not pure:

     float x = 3.14;
     import std.conv : to;
     auto y = x.to!string;


 ???

 Is there a reason for it not being pure? If not, this is a serious
 problem as this is such a fundamental function.


Probably because it uses C's float formatting functions, and they 
probably set errno and therefore aren't pure.

 Maybe because of floating point numbers uncertainty that would cause the
 resulting string to be different for two equivalent inputs? I can't seem
 to put an example together though.

No, it doesn't work like that.

Xinok <xinok live.com> writes:

On Saturday, 26 September 2015 at 17:08:00 UTC, Nordlöw wrote:
 Why is the following code not pure:

     float x = 3.14;
     import std.conv : to;
     auto y = x.to!string;


 ???

 Is there a reason for it not being pure? If not, this is a 
 serious problem as this is such a fundamental function.

I don't know the exact reason but I found a couple of functions 
which could be marked pure which are not, including 
strippedOctalLiteral and isOctalLiteralString. It's possible that 
some function was simply overlooked and needs to be marked pure 
or infer purity.

The larger issue at hand is that the compiler doesn't tell you 
where an impurity lies, merely that it exists. I mentioned this 
issue not too long ago while experiencing my own difficulties 
respecting purity.

Jack Stouffer <jack jackstouffer.com> writes:

On Saturday, 26 September 2015 at 17:08:00 UTC, Nordlöw wrote:
 Why is the following code not pure:

     float x = 3.14;
     import std.conv : to;
     auto y = x.to!string;


 ???

 Is there a reason for it not being pure? If not, this is a 
 serious problem as this is such a fundamental function.

Please make an issue on https://issues.dlang.org and I'll take a 
look a this later. Most of the functions in std.conv are 
templated so it must be some internal function that's not 
properly annotated, or it's using manual memory management.

=?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

On Sunday, 27 September 2015 at 05:52:26 UTC, Jack Stouffer wrote:
 Please make an issue on https://issues.dlang.org and I'll take 
 a look a this later. Most of the functions in std.conv are 
 templated so it must be some internal function that's not 
 properly annotated, or it's using manual memory management.

Already file here:

https://issues.dlang.org/show_bug.cgi?id=3437
https://issues.dlang.org/show_bug.cgi?id=4850