Regex for parsing complicated array

Question

I'm trying parse input string which looks like array[digit or expression or array, digit or expression or array] So I need to get values in [ , ]. I was trying to get them using this regex:

(array1)\[(.*),円(.*)\]

to get values of (.*) capturing groups, but it doen't work, because it's greedy quantifier, so in the case of:

array1[ array2[4,3] , array2[1,6] ]

I will get array2[4,3] , array2[1, as first capturing group and 6 as a second which is not right.

How can I get array2[4,3] as first and array2[1,6] as second capturing group? Or array2[array3[1,1],3] and 5+3 if the input string is array1[ array2[array3[1,1],3] , 5+3 ]?

Answer 1

You can make use of balancing groups:

array\d*\[\s*((?:[^\[\]]|(?<o>\[)|(?<-o>\]))+(?(o)(?!))),\s*((?:[^\[\]]|(?<o>\[)|(?<-o>\]))+(?(o)(?!)))\]

ideone demo on your last string.

A breakdown:

array\d*\[\s* # Match array with its number (if any), first '[' and any spaces
(
 (?: 
 [^\[\]] # Match all non-brackets
 |
 (?<o>\[) # Match '[', and capture into 'o' (stands for open)
 |
 (?<-o>\]) # Match ']', and delete the 'o' capture
 )+
 (?(o)(?!)) # Fails if 'o' doesn't exist
)
,\s* # Match comma and any spaces
( # Repeat what was above...
 (?: 
 [^\[\]] # Match all non-brackets
 |
 (?<o>\[) # Match '[', and capture into 'o' (stands for open)
 |
 (?<-o>\]) # Match ']', and delete the 'o' capture
 )+
 (?(o)(?!)) # Fails if 'o' doesn't exist
)
\] # Last closing brace

• rbrundritt: This fails if you add a third array.
• Jerry: @rbrundritt There's only one array with (at most) 2 sub arrays (but which can have more sub arrays) in the question. I'm not sure what you mean...?
• rbrundritt: Wouldn't it make more sense to allow it to work with any number of sub arrays.
• Jerry: @rbrundritt Then the capture groups wouldn't be needed. OP would have to make only one capture group containing all the sub arrays separated by comma in this condition.