Regex Question

[johnd]

How does newLISP control the value of system variables in regex? It seems they are set only on non-nil regex results.

> (regex ".*([aeiou]{2}).*" "Seattle")
("Seattle" 0 7 "ea" 1 2)
> $1
"ea"
> (regex ".*([aeiou]{2}).*" "San Francisco")
nil
> $1
"ea"
>

If this is the intended behavior it should probably be documented. I would argue that nil is a result and that $1 should return nil when the regex evaluates to nil. This was an issue recently because I was checking for $1 to be nil rather than the regex expression itself. The regex evaluated to nil but $1 retained a previous value.

John
[/i]

[cormullion]

Is this the same problem as I had?

http://www.alh.net/newlisp/phpbb/viewtopic.php?t=1948

[Jeff]

I disagree. I've put that side effect to good use in progressive logic. You can set $0 yourself between regexes. And you should always check the return value :)