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

[David Cole]

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
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