Re: [PATCH] More %define/%code encapsulation

[Paolo Bonzini]

> How about b4_percent_define_if_true instead?  Given that we have _ifdef, 
> _if seems like it ought to be like m4_if, which is not about booleans.

Yes.  OTOH we also have b4_flag_if.  Maybe b4_percent_define_flag_if, 
but these long macro names are getting more and more annoying to me.

> > - for _ifval, I'm thinking of
> >
> > m4_define([b4_class_name], [b4_get_percent_code([package])dnl
> > b4_get_percent_code_ifval([package], [.])$1])
>
> Why not the following?
>
>   m4_define([b4_class_name], [b4_percent_code_get([[package]])dnl
>   m4_ifval(b4_percent_code_get([[package]]), [.])$1])

Well, just because!  But if I want to be nitpicking, these are my reasoning:

- you "save more characters" than you show because it's 
b4_percent_code_ifval (you have one more _get).  If the names were 
shorter (omitting the _percent, for example...) the savings would be 
close to 50%!

- one less pair of parentheses.  m4 has already too many.

- quoting the if macros correctly is somewhat counterintuitive.

> To be clear, you mean that the no-value %define form:
>
>   %define my_boolean_variable
>
> is equivalent to:
>
>   %define my_boolean_variable "1"
>
> but you want it equivalent to:
>
>   %define my_boolean_variable ""

Using "1" for true is needlessly C-like.  In m4 (but also in the C 
preprocessor) it's common that "ifdef" marks whether a flag if true or 
false, without looking at the actual value.  Since the grammar's source 
code will not change, and the default is not documented (%define is not 
documented at all!!!), I find this change valuable.

Also, using a default of "" gives the least-surprise (compare with C) 
when the no-value form is used with a non-boolean variable.

Paolo