Re: proposal: simplify prologue alternatives into %code

[Paolo Bonzini]

> b. What Java user thinks "requires" means "imports"?  Yes, it makes sense 
> when you think about it, but isn't "imports" more obvious and easier to 
> remember?  Similarly, what Java user thinks "provides" means "additional 
> package-visible classes", which the epilogue handles anyway?  I wonder if 
> "requires" should be eliminated for Java.  In any case, I think these Java 
> issues demonstrate why it would be nice if the prologue alternatives were 
> not distinct grammar directives: developers of new skeletons wouldn't feel 
> as compelled to try to force their new square pegs into our old round 
> holes.

Okay, so we'd have only %code, %code "imports", and the epilogue.

I would love to have "%code" be synonym with a particular QUALIFIER, 
rather than a separate muscle.  Bonus points if you can make it 
skeleton-defined: so, in Java, %code would be synonym with %code 
"methods"; in C/C++, with %code "prototypes" (made up, but you get the 
idea).

Here is the implementation I suggest.  %code "foo" would append to the 
b4_code_blocks muscle something like

b4_code([foo], [...
])dnl

Note that all the code would go to the same muscle.
Then, c.m4 would do something like

b4_define_code([requires], [B4_DIVERT_REQUIRES])
b4_define_code([provides], [B4_DIVERT_PROVIDES])
b4_define_code([top], [B4_DIVERT_TOP])
b4_define_code_default([prototypes], [B4_DIVERT_PROTOTYPES])

b4_define_code would be defined like this in bison.m4

m4_define([b4_code], [m4_ifelse([$1], ]$1[, [$2], [])])dnl
m4_push_divert([$2])dnl
b4_code_blocks[]dnl
m4_pop_divert

and b4_define_code_default like this

m4_define([b4_code], [m4_ifelse([$1], ]$1[, [$2], [], [$2], [])])dnl
m4_push_divert([$2])dnl
b4_code_blocks[]dnl
m4_pop_divert

The code blocks would be recalled simply with m4_undivert.

> I propose that the former directive would *append* to any code already 
> associated with QUALIFIER; this would mimic the behavior of %{CODE%} and 
> of the existing prologue alternative directives.

Yes.

> 5. Hans suggested we drop the quotes around "QUALIFIER" or "NAME".  I 
> think that idea may have some merit, but lets debate this detail only 
> after resolving the larger issues here.

I have no real preference.

Paolo