regex to remove all whitespaces except between brackets

Question

I\'ve been wrestling with an issue I was hoping to solve with regex.

Let\'s say I have a string that can contain any alphanumeric with the possibility of a substrin

Answer 1

This doesn't sound like something you really want regex for. It's very easy to parse directly by reading through. Pseudo-code:

inside_brackets = false;
for ( i = 0; i < length(str); i++) {
    if (str[i] == '[' )
        inside_brackets = true;
    else if str[i] == ']'
        inside_brackets = false;
    if ( ! inside_brackets && is_space(str[i]) )
        delete(str[i]);
}

Anything involving regex is going to involve a lot of lookbehind stuff, which will be repeated over and over, and it'll be much slower and less comprehensible.

To make this work for nested brackets, simply change inside_brackets to a counter, starting at zero, incrementing on open brackets, and decrementing on close brackets.