The cool thing about Ka-Ping's Python example is that he builds regular expressions by combining objects. The label.*() method calls introduce labels into the regular expression which hold the data like your @ids. Addition combines regular expressions. Multiplication repeats them. Some symbolics like 'digit' are predefined, as well as functions like maybe() and anybut(). In this example he's parsing the output from 'ls'. I find this style more readable than even your heavily annotated updoc example.
At 02:19 PM 4/16/99 , Ka-Ping Yee wrote:
flag = member(letters, '-')
listing = (begline +
label.mode( flag + # file type flag*3 + flag*3 + flag*3) + # owner, group, world perms label.data( somespace + anything + # links, owner, grp, sz, date somespace + digit*2 + maybe(':') + digit*2 + # year or hh:mm somespace) + label.file( anybut('->')) + # anything before symlink maybe(label.link( somespace + '->' + anything)) + # possible symlink endline)
^\\(<mode>[A-Za-z-][A-Za-z-][A-Za-z-][A-Za-z-][A-Za-z-][A-Za-z-][A-Za-z-][A- Za-z-][A-Za-z-][A-Za-z-]\\)\\(<data>[ \011\015\012\014]+.*[
\011\015\012\014]+[0-9][0-9]\\(:\\)?[0-9][0-9][ \011\015\012\014]+\\)\\(<file>\\([^-]|-[^>]\\)*\\)\\(\\(<l ink>[ \011\015\012\014]+->.*\\)\\)?$>
>On Thu, 15 Apr 1999, Mark S. Miller wrote:
>> If I'd tried to write this without regex's, it might
>> be locally more readable, but would also be a lot more code -- an
>> interesting tradeoff. How does it compare with regex use in Perl or
>It looks pretty much par for the course, except for the cryptic
>(?ms) option in front and the unfamiliarity of the @bindings.
The (?m) flag allows multi-line input. The (?s) flag allows newlines to be
treated as a normal character, so that, for example, . will match it. (?x)
as mentioned in a previous message,
allows embedded whitespace and comments. If I wasn't worried about the installed base of expectations, I'd turn all these on by default. I'm puzzled why anyone would want them off.
>It's surprising how much it causes E to look like Perl. I guess
>even despite all the punctuation that Perl uses everywhere else,
>a sufficiently large fraction is in regular expressions to cause
>E-with-regexes to have a similar look.
Horrible though it may seem, given my goals, this is a good thing. Maximize contagion! Minimize incubation period!
>> Here's a readability test: By reading this code, can you easily tell what
>> syntax it parses?
>Not in a brief glance. I wanted to study it a little more before
>replying, but i thought i ought to point you at something i did a
>little while ago to make regular expressions more Python-like
How do you feel about the overly commented version?
I didn't understand your Python example.