Is it possible to use regular expressions to camelize/underscore strings?

Question

Is it possible to use nothing but Regular Expressions to convert strings like "hello_world" into "HelloWorld" and back?

I'm asking because I often need to create snippets for Sublime Text that automatically fills in "class_name" somewhere when I type "ClassName" somewhere else. I can only use perl-style regular expressions for this purpose.

Answer 1

Using perl regular expression:

hello_world -> HelloWorld

s/(_|\b)([a-z])/\u\2/g;

• \b: Match at boundary (space, start of string, punctuation mark, ..)
• [a-z]: lowercase alphabet
• \u: make uppercase for next character
• \2: group 2 (first lowercase character)
• (_|\b) -> group 1
• ([a-z]) -> group2

HelloWorld -> hello_world

s/([A-Z][a-z]+|[a-z]+)([A-Z])/\l\1_\l\2/g;

• Does not work for Hello.
• If you can use two substitutions, use s/([A-Z])/_\l\1/g; followed by s/^_//;