检查字符串是否是可能的正则表达式匹配的前缀

Question

I want to traverse a tree structure, but only those parts that match a wildcard expression, a la python glob, where double asterisk means 'any number of subdirs'.

For example, say my wildcard expression is /*/foo/**/bar/. This would match /a/foo/bar/, /b/foo/note/bar/, but not /a/bar/foo/bar/. You get the idea.

My problem is that when traversing the tree structure, I need to know whether the current dir could possibly match the wildcard expression as a prefix. So I do want to traverse the directory /a/, but not /a/bar/, because I know the latter will never match the wildcard expression.

The wildcard expression I will rewrite to a regular expression, of course.

Answer 1

Consider the following code for starters. I assume you have each "directory" in the path and pattern as elements in a pair of lists:

def traverse(pattern_list, path_list):
    if pattern_list[0] == '**':
        traverse_children(pattern_list, path_list[1:])
    if current_matches(pattern_list[0], path_list[0]):
        traverse_children(pattern_list[1:], path_list[1:])
        # Other things you might want to do in the case of a valid prefix

def current_matches(pattern_atom, path_atom):
    return pattern_atom in (path_atom, '*', '**')