Greediness of quantified subpatterns

Q

What is the greediness of quantified subpatterns? What does it mean that a quantified subpattern is "greedy"?

How to show that a quantified subpattern is "greedy" on this PHP script: if ($t=10): echo "Just started...!"; endif; if ($t=11): echo "Hungry!"; endif; if ($t=12): echo ""Ah, lunch-time!"; endif;?

✍: FYIcenter.com

A

The greediness of quantified subpatterns is referring to the behavior on when to stop repeating a quantified subpattern in the matching process.

By default, a quantified subpattern is "greedy", that is, it will match as many times as possible (given a particular starting location) while still allowing the rest of the pattern to match.

For example: when applying pattern /a+a/ to "aaaa", the quantified subpattern /a+/ will, by default, match the first 3 characters "aaa" which still allowing the next subpattern /a/ to match the last character "a". In other words,

(a+)a   # matches 'aaaa' with $1='aaa', not $1='a'

The regular expression to show the greediness of a quantified subpattern on the given PHP script:

(if .+ endif;)

if - matches 'if'
.+ endif; - matches as many characters as possible 
            while 'end if;' is at the end

Click the button to test this regular expression here online:

2013-01-26, 2031👍, 0💬