From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2013-04-19T03:09:23+09:00
Subject: Re: Match against multiple patterns problem

On Thu, Apr 18, 2013 at 7:40 PM, Charles Hixson
<charleshixsn@earthlink.net> wrote:
> What I would want to do, if it were legal code would be:
>         if    not s.is_a?(String)    or    len(s) < 1    then    return
> ["1",""]
>         if    (m = /^[^\W_]+/.match(s) ) !== nil    then    return    ["a",
> m[0]]
>         elsif    (m = /^\s+/.match(s) ) != nil      then    return    ["s",
> m[0]]
>         elsif    (m = /^[[:cntrl:]]+/) != nil       then    return    ["c",
> m[0]]
>         elsif    (m = /^[[:punct:]_]+/) != nil      then    return    ["p",
> m[0]]
>         elsif    (m = /^[^\w\s[:cntrl:][:punct:]]+/) != nil
>                                                     then    return    ["r",
> m[0]]
> But this isn't legal, because one can't do an assignment within a logic test
> (any expression?).
> So what SHOULD I do?  I can double the length of the code by pulling the
> assignments out, and
> interleaving tests and assignments, but that's ugly (i.e., it makes the code
> harder to read).  Any better choices?

Actually you can do assignments inside logical expressions. The
problems in the code above are related to nonexistent methods (len),
operator precedence(not and or) and a typo (!==). Try this:

if (!s.is_a?(String) || (s.length < 1))
    return    ["1",""]
end
if  (m = /^[^\W_]+/.match(s) ) != nil    then    return    ["a", m[0]]
elsif (m = /^\s+/.match(s) ) != nil      then    return    ["s", m[0]]
elsif (m = /^[[:cntrl:]]+/) != nil       then    return    ["c", m[0]]
elsif (m = /^[[:punct:]_]+/) != nil      then    return    ["p", m[0]]
elsif (m = /^[^\w\s[:cntrl:][:punct:]]+/) != nil then    return    ["r", m[0]]
end

Changing the returns for puts to test outside a method:

1.9.2p290 :116 > s = "   "
 => "   "
1.9.2p290 :117 > if (!s.is_a?(String) || (s.length < 1))
1.9.2p290 :118?>       puts    ["1",""]
1.9.2p290 :119?>   end
 => nil
1.9.2p290 :120 > if  (m = /^[^\W_]+/.match(s) ) != nil    then    puts
   ["a", m[0]]
1.9.2p290 :121?>   elsif (m = /^\s+/.match(s) ) != nil      then
puts    ["s", m[0]]
1.9.2p290 :122?>   elsif (m = /^[[:cntrl:]]+/) != nil       then
puts    ["c", m[0]]
1.9.2p290 :123?>   elsif (m = /^[[:punct:]_]+/) != nil      then
puts    ["p", m[0]]
1.9.2p290 :124?>   elsif (m = /^[^\w\s[:cntrl:][:punct:]]+/) != nil
then    puts    ["r", m[0]]
1.9.2p290 :125?>   end
s


It's not very pretty still, but at least it works. I'm sure someone
will come up with a more elegant solution.

Jesus.