Denis Koroskin wrote:
On Thu, 19 Feb 2009 18:01:56 +0300, Andrei Alexandrescu
<[email protected]> wrote:
bearophile wrote:
Andrei Alexandrescu:
but most regex code I've seen mentions the string first and the
regex second. So I dropped that idea.<
I like the following syntaxes (the one with .match() too):
import std.re: regex;
foreach (e; regex("a[b-e]", "g") in "abracazoo")
writeln(e);
foreach (e; regex("a[b-e]", "g").match("abracazoo"))
writeln(e);
auto re1 = regex("a[b-e]", "g");
foreach (e; re1.match("abracazoo"))
writeln(e);
auto re1 = regex("a[b-e]", "g");
foreach (e; re1 in "abracazoo")
writeln(e);
These all put the regex before the string, something many people would
find unsavory.
----------------
I like the support of verbose regular expressions too, that ignore
whitespace and comments (for example with //...) inserted into the
regex itself. This simple thing is able to turn the messy world of
regexes into programming again.
This is an example of usual RE in Python:
finder =
re.compile("^\s*([\[\]])\s*([-+]?\d+)\s*,\s*([-+]?\d+)\s*([\[\]])\s*$")
This is the same RE in verbose mode, in Python still (# is the
Python single-line comment syntax):
finder = re.compile(r"""
^ \s* # start at beginning+ opt spaces
( [\[\]] ) # Group 1: opening bracket
\s* # optional spaces
( [-+]? \d+ ) # Group 2: first number
\s* , \s* # opt spaces+ comma+ opt spaces
( [-+]? \d+ ) # Group 3: second number
\s* # opt spaces
( [\[\]] ) # Group 4: closing bracket
\s* $ # opt spaces+ end at the end
""", flags=re.VERBOSE)
As you can see it's often very positive to indent logically those
lines just like code.
Yah, I saw that ECMA introduced comments in regexes too. At some point
we'll implement that.
----------------
As the other people here, I don't like the following much, it's a
misleading overload of the ~ operator:
"abracazoo" ~ regex("a[b-e]", "g")
----------------
I don't like that "g" argument much, my suggestions:
RE attributes:
"repeat", "r": Repeat over the whole input string
"ignorecase", "i": case insensitive
"multiline", "m": treat as multiple lines separated by newlines
"verbose", "v": ignores space outside [] and allows comments
And how do you combine them? "repeat, ignorecase"? Writing and parsing
such options becomes a little adventure in itself. I think the "g",
"i", and "m" flags are popular enough if you've done any amount of
regex programming. If not, you'll look up the manual regardless.
Perhaps, string.match("a[b-e]", Regex.Repeat | Regex.IgnoreCase); might
be better? I don't find "gmi" immediately clear nor self-documenting.
I got disabused a very long time ago of the notion that everything about
regexes is clear or self-documenting. Really. You just get to a level of
understanding that's appropriate for your needs. On that scale, getting
used to "gmi" is so low, it's not even worth discussing.
Andrei
