Re: simple regexp problem

Square brackets don't mean what you think they mean. Use (?:...) to group things without capturing, and use the ? suffix to make something optional.

/^(\w+)(?:_(\w+))?$/
[download]

Comment on Re: simple regexp problem Select or Download Code

Replies are listed 'Best First'.
Re^2: simple regexp problem by ikegami (Patriarch) on Dec 05, 2005 at 17:46 UTC
Ah shoot! While the advice in the above post is sound, the code won't work because "`\w`" includes "`_`"! Fix: `/^([a-zA-Z0-9+])(?:_(\w+))?$/` [download] or `/^((?:(?!_)\w)+)(?:_(\w+))?$/` [download]	[reply] [d/l] [select]
Re^3: simple regexp problem by jeanluca (Deacon) on Dec 06, 2005 at 13:36 UTC
This works too: `/^(\w+?)(?:_(\w+))?$/` But why the last ? ? If I leave it off, it doesn't parse the string "AAAAAAA" Thanks Luca	[reply] [d/l]
Re^4: simple regexp problem by ikegami (Patriarch) on Dec 06, 2005 at 15:31 UTC
`atom?` (as opposed to `atom??`, `atom*?` and `atom+?`) means `atom` is optional. In other words, it provides the "optionally" in "you want AAAAAA optionally followed by _BBBBBB".	[reply] [d/l] [select]