Why can't Regular Expressions use keywords instead of characters?

Question

Okay, I barely understand RegEx basics, but why couldn\'t they design it to use keywords (like SQL) instead of some cryptic wildcard characters and symbols?

Is it for pe

Answer 1

You really want this?

Pattern findGamesPattern = Pattern.With.Literal(@"<div")
    .WhiteSpace.Repeat.ZeroOrMore
    .Literal(@"class=""game""").WhiteSpace.Repeat.ZeroOrMore.Literal(@"id=""")
    .NamedGroup("gameId", Pattern.With.Digit.Repeat.OneOrMore)
    .Literal(@"-game""")
    .NamedGroup("content", Pattern.With.Anything.Repeat.Lazy.ZeroOrMore)
    .Literal(@"<!--gameStatus")
    .WhiteSpace.Repeat.ZeroOrMore.Literal("=").WhiteSpace.Repeat.ZeroOrMore
    .NamedGroup("gameState", Pattern.With.Digit.Repeat.OneOrMore)
    .Literal("-->");

Ok, but it's your funeral, man.

Download the library that does this here:
http://flimflan.com/blog/ReadableRegularExpressions.aspx

Answer 2

Well, if you had keywords, how would you easily differentiate them from actually matched text? How would you handle whitespace?

Source text Company: A Dept.: B

Standard regex:

Company:\s+(.+)\s+Dept.:\s+(.+)

Or even:

Company: (.+) Dept. (.+)

Keyword regex (trying really hard not get a strawman...)

"Company:" whitespace.oneplus group(any.oneplus) whitespace.oneplus "Dept.:" whitespace.oneplus group(any.oneplus)

Or simplified:

"Company:" space group(any.oneplus) space "Dept.:" space group(any.oneplus)

No, it's probably not better.

Answer 3

I don't think keywords would give any benefit. Regular expressions as such are complex but also very powerful.

What I think is more confusing is that every supporting library invents its own syntax instead of using (or extending) the classic Perl regex (e.g. \1, $1, {1}, ... for replacements and many more examples).

Answer 4

For some reason, my previous answer got deleted. Anyway, i thing ruby regexp machine would fit the bill, at http://www.rubyregexp.sf.net. It is my own project, but i think it should work.

Answer 5

It's actually pretty easy to implement a "wordier" form of regex -- please see my answer here. In a nutshell: write a handful of functions that return regex strings (and take parameters if necessary).

Answer 6

I know its answering your question the wrong way around, but RegExBuddy has a feature that explains your regexpression in plain english. This might make it a bit easier to learn.