Re: optimize lt_combine

[Gary V. Vaughan]

Hi Eric,

On 17 Oct 2007, at 19:25, Eric Blake wrote:
> I liked the concept of lt_combine so much that I added m4_combine  
> to m4sugar.
> In the process,

Thanks :-)

A while ago I considered shipping the useful stuff from m4sugar and  
ltsugar
with m4 2.0... it might also give us some scope for speeding up some  
of the
stickier implementations by moving them into a module in C.

> I made some optimizations and some slight semantic changes:
>
>  - the separator is now used literally, rather than losing  
> whitespace after
> comma
>  - the infix argument is now used literally, rather than undergoing  
> expansion
> (consider m4_define([_],[oops])...)
>  - the quoting in m4_foreach is fixed (consider m4_define 
> ([_Lt_suffix])...)
>  - useless use of m4_car is avoided, and the m4_shiftn(3, $@) is  
> now inlined
> and done once up front, rather than once per _Lt_prefix
>  - the separator is no longer defaulted, so you can use an empty  
> separator
>  - the suffix list can now include an empty suffix, so the caller  
> must be
> taught not to pass an empty suffix to preserve previous usage pattern
>    + _lt_decl_varnames_tagged was the only caller for now, so I  
> optimized it as
> well
>    + right now, lt_decl_varnames_tagged is never called with more  
> than one
> argument.  It looks like it may have been intended to be called  
> with multiple
> VARNAME arguments, rather than a single argument consisting of  
> multiple
> VARNAMEs, but changing that is more invasive.  So for now I just  
> added an
> assert which will trigger if we ever change our minds, to remind us  
> to fix the
> usage patterns appropriately.

All good!

> OK to apply?

I'm writing the testcase for the last release blocker today, and  
would rather
hold off on this until we've rolled the release personally.  But it  
is no more
intrusive than the lt_join optimisations Ralf agreed to, so if  
someone else
wants to overrule and let you apply, I won't be heartbroken :-)

Cheers,
        Gary
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