[cmake-developers] $LIST_LENGTH{} syntax

[Brad King]

On 1/22/19 10:55 AM, Marc CHEVRIER wrote:
> What about introducing a syntax similar to the version comparison:
> 
>   * LENGTH_EQUAL
>   * LENGTH_GREATER
>   * LENGTH_LOWER
>   * etc…
> 
> To use it:
> if (my_list LENGTH_EQUAL 1)
>   # do my stuff
> endif()

That's where this thread started.  Every new if() operator potentially
requires a policy, and there may be other places that the length of
a list is useful.

> Or introduce a more general syntax for list management as part
> of an expression:
> $LIST{<op>,<list>[,<arg>,…]}
> 
> Where <op>, <list> and <arg> use same semantic as list command.
> To use it:
> of ($LIST{LENGTH,my_list} EQUAL 1)
>   # do my stuff
> endif()

Yes, something more extensible would be fine.  We need to be careful
not to slow down the variable reference syntax parser though.

-Brad