Regular Expressions to Split Lists Into Sub-Lists

Regular Expressions to Split Lists Into Sub-Lists

Post by Yimin Ron » Tue, 19 Aug 2008 04:33:08


For example, given a string "A, B, C (P, Q, R), D (X, Y [K, L, M ,N],
Z)".

Would like to split into tokens thusly:

a[0] == "A"
a[1] == "B"
a[2] == "C (P, Q, R)"
a[3] == "D (X, Y [K, L, M ,N], Z)"

i.e. do not descend into sub-lists

PHP split() using commas as a delimiter will give 14 tokens.

I can write a routine which checks the input byte by byte and
increments or decrements a counter based on how many opening "( [ {"
or closing ") ] }" brackets it sees. If counter > 0, this means ignore
delimiters (i.e. keep looking). Guaranteed to work, but to my mind
seems to be rather clunky.

Is it possible to extract the tokens using regular expressions? E.g.
substitute highest level commas with a special delimiter say "~", and
split using that delimiter.

Thanks for reading.

Regards,

YR
 
 
 

Regular Expressions to Split Lists Into Sub-Lists

Post by Yimin Ron » Wed, 20 Aug 2008 02:03:35


Agreed, however the step I need is to replace top level delimiters in
the input. Do you think regular expression substitution can do this? /
YR