Re: listing currently defined macros

[Gary V. Vaughan]

Hi Eric,

On 19 Feb 2008, at 02:19, Eric Blake wrote:

According to Gary V. Vaughan on 2/17/2008 2:07 AM:

Hi Gary, and thanks for a review of my ideas, plus some cool ones of your own.

What a team! Glad you like :-)

| However (breaking my own rule about not introducing additional macros if | at all possible), I think list sorting and filtering are both useful enough | idioms that we should break them out into new builtins so that our users | needn't resort to the hackish things you mention below... which merely

| highlight deficiencys in the current language implementation.  Also,

| symbols is not important.  So:
|
|  -- Builtin (gnu): m4symbols([NAMES...])

|      quoted.


we could then do:

define(`dumpdef', `builtin(`dumpdef', sort(m4symbols))')

to recover the former behavior.

| m4symbols proper will be faster in the case where the order of returned | With no arguments, `m4symbols' expands to a unordered, comma- separated | list of the names of all currently defined macro. Each macro name is In other m4 implementations (I tested Solaris and OpenBSD), dumpdef output is also unordered - it is only ordered on GNU. But I would be okay with a documented change to dumpdef behavior to be unordered, particularly since

That's interesting... yes, most definitely.

|  -- Builtin (list): sort(NAME, [...])

|      This macro was added in M4 2.0.

At which point, the user can easily create:

define(`cmp', `ifelse(`$1', `$2', `0',
~                      (sort(`$1', `$2')), `($1,$2)', `-1',
~                      `1')')

| Expands to a sorted, comma-separated list of quoted NAME arguments.

dsos :-)

Or, we can define it for them in a directory module of m4 with supporting

|  -- Builtin (list): uniq(NAME, [...])
|      Expands to an unordered, comma-separated list of quoted NAME
| arguments,

|      listed in the expansion.  This macro was added in M4 2.0.
|
|      uniq(m4symbols(`ifndef', `ifdef', `define', `define', `ifdef',
| `undef'))
|      =>ifdef,define,ifdef

Don't you mean
~ =>ifndef,define,ifdef

| with only the first occurrence of duplicate consecutive parameters

No no. There is no ifndef builtin, so m4symbols expands to:

   `ifdef',`define',`define',`ifdef'


so the two ifdefs are both kept.

But (for ease of implementation) uniq only discards consecutive duplicates,

|  -- Builtin (list): filter(PATTERN, LIST, [PATSYNTAX])

|      Changeresyntax::) or PATSYNTAX if passed.
|
|      define(`dquote', ``$@'')
|      =>
|      sort(filter(`*def*', dquote(m4symbols), `GLOB'))
|      =>define,defn,dumpdef,ifdef,popdef,pushdef,undefine

Hmm.  This would be the first builtin that takes a quoted list of
elements.  Maybe it would be worth also making dquote builtin:

- -- Builtin (list): dquote(ELEMENT, ...)
~  Expand to a quoted, comma-separated list of quoted list ELEMENTs.


(which can be implemented, but requires a foreach loop).

| Expands to an unordered, comma-separated list of quoted LIST elements | that match PATTERN, either according to the current RESYNTAX (*note so that you could use dquote regardless of the current quoting characters (in your example, it would only work with `'). Then again, dquote is easy to implement efficiently without needing another builtin, unlike filter

lists, and having a quote agnostic dquote is a good plan.


expanded-quote character in the definition of a macro, which turns into

much yet, but maybe a reverse syntaxtable lookup builtin:

 -- Builtin (gnu): syntax(SYNTAX-CATEGORY)
     Expand to a quoted, comma-separated list of quoted syntax table
     entries that have SYNTAX-CATEGORY.  SYNTAX-CATEGORY is one of the
     letters used to change syntax with the `changesyntax' builtin
     (*note Changesyntax::).

Ofcourse the problem with this idea is how we deal with unbalanced quote
characters.  Otherwise, I like the introspection it provides.

I agree. Eventually we should try to be kind to users passing around quoted Although, perhaps (as part of the plan to level the playing field between C builtins and m4 macros) we should provide some means to write a not- yet- whatever is a valid quote at expansion time. I haven't thought about this

| I'm sure we can implement several of the m4sugar style list mangling macros | eventually, hence I've put these new builtins into a separate list module.

up such a module.

Sounds like a good idea to me. I'll see if I can get some time to write

Excellent! :-D

|> So maybe you could argue that we already have
|> globbing if you can just translate the pattern correctly).
|
| I think this proposal has that covered.

I like the idea of using 'GLOB' as another regex syntax, although it
implies some intelligence in the underlying regex builtins (either we
would do glob->regex translation ourselves, or we would have to decide
between re_search vs. fnmatch).

I think the latter will better build on existing proven code, and can
probably be factored somewhat to prevent duplication among builtin
implementations.

Cheers,
        Gary
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