[luatex] [OT] The consumption of an input string.

[Paul Isambert]

Hello all,

This is not really a LuaTeX question, but I ask it here anyway since a
lot of knowledgeable people read this list.

I’ve been surprised to discover that

    print(string.gsub('abc', '.*', '(%0)'))

returns

    (abc)()

(similarly, “string.gmatch('abc', '.*')” returns two matches). I’d
expect

    (abc)

since the string is completely consumed after the first match and
there’s no reason to try matching any further. I thought it was a Lua
quirk but then in Ruby

    puts 'abc'.gsub(/.*/, '(\0)')

returns the same thing. On the other hand, “(abc)” is returned as
expected (by me) with

    echo substitute('abc', '.*', '(\0)', 'g')

in Vim script and

    import re
    print re.sub(re.compile('(.*)'), '(\\1)', 'abc')

in Python and

    echo "abc" | sed 's/.*/(\0)/g'

with sed (I’m not familiar with Python and sed, so the last two codes
are only tentative).

Now, my knowledge in programming languages being what it is, I might
be confused by something obvious; if anybody could shed some light,
I’d be grateful.

Best,
Paul