Re: Patch to check for required programs when building from source checkout

[Eric Blake]

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According to Pádraig Brady on 10/21/2008 4:04 PM:
>     echo "$ver" | sed '
>       s/^\([0-9]\{,\}\)\.\([0-9]\{,\}\)[.0]*$/\1.\2.0/;         #1.10  -> 
> 1.10.0
>       s/^\([0-9]\{,\}\)\.\([0-9]\{,\}\)\([a-z]\)/\1.\2.99\3/;   #1.10a -> 
> 1.10.99a

For what it's worth, Autoconf does this by converting \([0-9]+\)\([a-z]+\)
to \1+1, -1, radix36(\2).  In other words, 1.10a becomes 1.11.-1.10.

- From there, it is a simple numerical comparison, supplying a 0 for any
implicit field, and declaring results at the left-most field that differs:
 1.10.x < 1.11.-1.x, but 1.11.-1 < 1.11.0

Hmm.  Since bootstrap requires the existence of autoconf, why not just use
autoconf, instead of reimplementing this in sed?

echo 'm4_divert(0)m4_version_compare('$ver,$prereq')' \
  | autom4te --language=m4sugar -

outputs -1 if $ver is smaller, 0 if equal, 1 if greater than $prereq.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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