[CMake] functions as first class objects

[Michael Wild]

On 19. Nov, 2009, at 15:44 , Jed Brown wrote:

> Michael Wild wrote:
>>
>> On 19. Nov, 2009, at 15:06 , Jed Brown wrote:
>>
>>> Michael Wild wrote:
>>>
>>>> Not sure I'd like that... Instead of being more expressive, I  
>>>> think this
>>>> would be very confusing.
>>>
>>> This is not a some magic beast coming out of functional  
>>> languages.  In
>>> fact, it's pretty hard to find a language that can't do this sort of
>>> thing, even older Fortrans let you pass functions.
>>>
>>> Jed
>>
>> Yes, but that's something completely different! It's not like you're
>> able to do (using your notation):
>
> (not my notation)
>
>> set(&tmp &install)
>> set(&install &add_executable)
>> set(&add_executable &tmp)
>>
>> In C/C++ and to various extent in Fortran (depending on the  
>> version) you
>> can pass around "function pointers". This is _not_ a function.  
>> There's
>> no way of doing that in C/C++ or Fortran (that is, without using ugly
>> preprocessor magic).
>
> CMake is untyped where as C, for example, is statically typed and only
> allows symbols to be defined once (C++ breaks this with templates, but
> you're supposed to be careful so that all definitions are equivalent).

Although this is OT, I have to say that this is not true. C++ is still  
statically typed. You can overload functions, but then it really is  
the same thing as the function signature is considered to be part of  
the name. Also templates do not change this, as the template  
parameters are part of the type name.

> In any case, you sure can do
>
>  int (*Func)(int,int) = SomeFunction;
>  int x = Func(5,6);
>  int y = FoldL(Func,array,size,3);
>
> and so on.
>

Sure, but you're not _renaming_ a function. You're just assigning the  
address of a function to a pointer which can then be used to invoke  
that function. It is _always_ clear that Func is a pointer to a  
function and not something else.

> Jed
>

Anyways, I didn't want to get into a language-war, but rather voiced  
my dislike for such dubious flexibility. CMake is very domain-specific  
language used to create build systems, not a general-purpose language.

BTW, in the OP's particular case I would prefer to patch the upstream  
source without any voodoo.

Michael