Is there a nice way to evaluate a regular expression range, say, for a url such as
http://example.com/[a-z]/[0-9].htm
This would be converted into:
http://example.com/a/0.htm
http://example.com/a/1.htm
http://example.com/a/2.htm
...
http://example.com/a/9.htm
...
http://example.com/z/0.htm
http://example.com/z/1.htm
http://example.com/z/2.htm
...
http://example.com/z/9.htm
I've been scratching my head about this, and there's no pretty way of doing it with开发者_运维问答out going through the alphabet and looping through numbers.
Thanks in advance!
If you really need to do this, it's not that hard to generate the strings using recursion. Here's a snippet to do just that in Java:
public class Explode {
static void dfs(String prefix, String suffix) {
final int k = suffix.indexOf('[');
if (k == -1) {
System.out.println(prefix + suffix);
} else {
prefix += suffix.substring(0, k);
char from = suffix.charAt(k+1);
char to = suffix.charAt(k+3);
suffix = suffix.substring(k+5);
for (char ch = from; ch <= to; ch++) {
dfs(prefix + ch, suffix);
}
}
}
public static void main(String[] args) {
String template = "http://example.com/[a-c]/[0-2][x-z].htm";
dfs("", template);
}
}
(see full output)
This is a standard recursive tuple generator, but with some string infixing in between. It's trivial to port to C#. You'd want to use a mutable StringBuilder
-like class for better performance.
I guess there is no way to expand regular expressions in general. Your example
http://foo.com/[a-z]/[0-9].htm
is a very easy regex without *
or +
for instance. How would you expand such a regex?
In your case you might get away with some loops, but as I said - this is a untypical (easy) regex.
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