On Wed, 4 Jul 2012, Eric Blake wrote:
On 07/04/2012 12:58 AM, Vincent Torri wrote:
On Mon, 2 Jul 2012, Eric Blake wrote:
Not directly with a single m4_foreach_w, but it would be possible with
other macro constructs. Note that m4 is better suited for
comma-separated lists instead of whitespace-separated lists,
when you say 'better suited', you mean faster ?
Yes. m4_foreach_w is more or less a wrapper that converts spaces into
commas, then calls m4_foreach on the comma-separated result. Starting
with comma-separated lists in the first place can use native m4 handling
rather than having to do under-the-hood conversions.
I ask because I used a simple macro that uses m4_foreach_w. Should I use
m4_foreach instead ?
That all depends on the syntax you want your users to be aware of.
There are some cases where whitespace-separated lists are easier for
users to type. Furthermore, in autoconf particularly, there is a
benefit to using whitespace separation when you are interacting with
shell code output (for example, having the flexibility to write 'for i
in $1; do', but also do m4 processing on each element of $1). In other
words, the trade-off between m4 speed and ease of use is not always trivial.
as I'm the maintainer of the autotools, I use the syntax I want. I just
want to call m4 macro for all the tokens, so using a comma separated list
is fine.
thank you
Vincent Torri
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