Re: POSIX vs. eval

[Gary V. Vaughan]

On 3 Jan 2007, at 14:31, Eric Blake wrote:
> Hi Gary, and happy new year,

A Happy New Year to you and all M4teans :-)

> According to Gary V. Vaughan on 12/29/2006 1:27 PM:
> > I think the only change in the POSIX wording would be to remove
> > the forbid aspect, and instead list all the required operators.
>
> Here's the aardvark I finally submitted:
> https://www.opengroup.org/sophocles/show_mail.tpl? 
> CALLER=index.tpl&source=L&listname=austin-review-l&id=2250

Perfect!

> In preparing the aardvark, I also realized that it may be worth  
> adding the
> following GNU extension in m4 2.0.  Currently, if eval encounters a  
> word
> (ie. macro name), it is a syntax error.  But we could check if the
> definition of that macro is a number, and thus support variables; once
> variables are supported, we can then also support assignment  
> operators.
> Thus "define(a,1)ifelse(eval(`a++'))a" would expand to "2", similar  
> to the
> shell construct "a=1; : $((a++)); echo $a".

Ooo!  Yes indeed, that would certainly be a very powerful addition to
the m4 toolkit :-)  Nice job.

Cheers,
        Gary
--
Gary V. Vaughan      ())_.  address@hidden
Research Scientist   ( '/   http://blog.azazil.net
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