[cmake-developers] if (FOO == BAR) ...

[Clinton Stimpson]

Is there a best practices using existing functionality to always avoid 
automatic dereference when comparing strings?

Clint

On Thursday, March 21, 2013 02:56:51 PM David Cole wrote:
> Unfortunately, this entire discussion nicely demonstrates and
> reinforces my belief that we ought not to do this == thing...
> 
> If Alex, Brad, Matthew and I can't understand each other's meanings
> within the context of this discussion, what chance does a poor user
> reading through the CMake IF documentation have of getting it right?
> 
> Adding a new better way to do something without eliminating the old
> not-so-good way of doing the same thing is not necessarily a good
> thing. Multiple ways to do things just make people shake their heads
> and ask "Why?"
> 
> I am still voting no on this one.
> 
> 
> David C.
> 
> 
> -----Original Message-----
> From: Alexander Neundorf <neundorf at kde.org>
> To: cmake-developers <cmake-developers at cmake.org>
> Sent: Thu, Mar 21, 2013 2:43 pm
> Subject: Re: [cmake-developers] if (FOO == BAR) ...
> 
> On Thursday 21 March 2013, Matthew Woehlke wrote:
> > On 2013-03-20 17:42, Alexander Neundorf wrote:
> > > On Wednesday 20 March 2013, Matthew Woehlke wrote:
> > >> On 2013-03-20 17:10, David Cole wrote:
> > >>> Are you proposing that == behaves as STREQUAL, or as EQUAL?
> > >> 
> > >> What's the difference?
> > >> 
> > >> Okay, for <, >, there is an obvious answer, but for ==, I am
> 
> trying and
> 
> > >> failing to think of a situation where treating the arguments as
> 
> numbers
> 
> > >> would give a different result vs. treating them as strings.
> > > 
> > > E.g. "0" vs. "0.0"
> > 
> > Is "0.0" a floating-point number or a version string? In the context
> 
> of
> 
> > CMake, I would have rather expected it to be the latter. (Does CMake
> > even understand floating point?) If '==' assumes numbers, how do I
> 
> tell
> 
> > it I really meant a version string?
> 
> EQUAL tries to convert to double:
> 
>   if (argP1 != newArgs.end() && argP2 != newArgs.end() &&
>         (*(argP1) == "LESS" || *(argP1) == "GREATER" ||
>          *(argP1) == "EQUAL"))
>         {
>         def = cmIfCommand::GetVariableOrString(arg->c_str(), makefile);
>          def2 = cmIfCommand::GetVariableOrString((argP2)->c_str(),
> makefile);
>         double lhs;
>         double rhs;
>         bool result;
>         if(sscanf(def, "%lg", &lhs) != 1 ||
>            sscanf(def2, "%lg", &rhs) != 1)
> 
> 
> My "==" implementation simply compares the strings on both sides in the
> most
> simple and straightforward way.
> 
> 
> Alex
> --
> 
> Powered by www.kitware.com
> 
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
> 
> Please keep messages on-topic and check the CMake FAQ at:
> http://www.cmake.org/Wiki/CMake_FAQ
> 
> Follow this link to subscribe/unsubscribe:
> http://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers
> 
> 
> --
> 
> Powered by www.kitware.com
> 
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
> 
> Please keep messages on-topic and check the CMake FAQ at:
> http://www.cmake.org/Wiki/CMake_FAQ
> 
> Follow this link to subscribe/unsubscribe:
> http://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers
-- 
Clinton Stimpson
Elemental Technologies, Inc
Computational Simulation Software, LLC
www.csimsoft.com