How to match the main subgroup in a regular expression? - regex

Question

Having this string:
"example( other(1), 123, [25]).othermethod(456)"
How i can capture only the arguments of the main functions:
"other(1), 123, [25]" and "456"
I am trying this:
http://regex101.com/r/cR0uS9/2
In html example. Having this:
<div>
<div>
<div>12</div>
<div>34</div>
</div>
</div>
<div>56</div>
I want to get:
<div>
<div>12</div>
<div>34</div>
</div>
and 56 as second match.

Answer 1

Here's a pattern that doesn't use recursion:
\w+\s*\((?P<parameters>(?:(?:(?:[^()]*\([^()]*\))+|[^()]*)(?:,(?!\s*\))|(?=\))))*)\)
Caveats:
Does not support more than 2 levels of nested braces. e.g.
a(b(c()))
Strings containing ( or ) will trip it up. e.g.
a(")")
You'll find the parameters in the group called "parameters".
Demo.
Explanation:
\w+ # function name
\s* # white space
\(
(?P<parameters> # parameters:
(?:
# two possibilities: 1: a simple parameter, like "12", "'hello'", or "3*1+2"
# 2: the parameter contains braces.
# we'll try to consume pairs of braces. If that fails, we'll simply match a parameter.
(?:
(?: # match a pair of braces ()
[^()]*
\(
[^()]*
\)
)+ # consume as many pairs of braces as possible. Make sure there's at least one, though, because we can't go matching nothing.
|
[^()]* # since there are no more (pairs of) braces, simply consume the function's parameters.
)
# next, either consume a "," or assert there's a ")"
(?:
,
(?! # make sure there is another parameter after the comma
\s*
\)
)
|
(?=
\)
)
)
)*
)
\)
P.S.: I haven't managed to come up with an acceptable pattern for the HTML example yet.

Answer 2

This does some recursion. Use it in a global find function.
# '~(?is)(?:([a-z]\w*)\s*\(((?&core)|)\))(?(DEFINE)(?<core>(?>(?&content)|(?:[a-z]\w*\s*\(|\()(?:(?=.)(?&core)|)\))+)(?<content>(?>(?![a-z]\w*\s*\(|[()]).)+))~'
(?xis-)
(?:
( [a-z] \w* ) # (1), Start-Delimiter, Function
\s* \(
( # (2), CORE
(?&core)
|
)
\) # End-Delimiter, close paren
)
# ///////////////////////
# // Subroutines
# // ---------------
(?(DEFINE)
# core
(?<core>
(?>
(?&content)
|
(?: # Start-Delimiter
[a-z] \w* \s* \( # Function
| \( # Or, a open paren
)
(?:
(?= . )
(?&core) # Recurse core
|
)
\) # End-Delimiter, close paren
)+
)
# content
(?<content>
(?>
(?!
[a-z] \w* \s* \(
| [()]
)
.
)+
)
)
Output:
** Grp 0 - ( pos 0 , len 29 )
example( other(1), 123, [25])
** Grp 1 - ( pos 0 , len 7 )
example
** Grp 2 - ( pos 8 , len 20 )
other(1), 123, [25]
** Grp 3 - NULL
** Grp 4 - NULL
-----------------------
** Grp 0 - ( pos 30 , len 16 )
othermethod(456)
** Grp 1 - ( pos 30 , len 11 )
othermethod
** Grp 2 - ( pos 42 , len 3 )
456
** Grp 3 - NULL
** Grp 4 - NULL
For the html div -
# '~(?s)(?:<div>((?&core)|)</div>)(?(DEFINE)(?<core>(?>(?&content)|<div>(?:(?=.)(?&core)|)</div>)+)(?<content>(?>(?!</?div>).)+))~'
(?xs-)
(?:
<div> # Start-Delimiter <div>
( # (1), CORE
(?&core)
|
)
</div> # End-Delimiter </div>
)
# ///////////////////////
# // Subroutines
# // ---------------
(?(DEFINE)
# core
(?<core>
(?>
(?&content)
|
<div> # Start-Delimiter <div>
(?:
(?= . )
(?&core) # Recurse core
|
)
</div> # End-Delimiter </div>
)+
)
# content
(?<content>
(?>
(?! </?div> )
.
)+
)
)
Output:
** Grp 0 - ( pos 0 , len 82 )
<div>
<div>
<div>12</div>
<div>34</div>
</div>
</div>
** Grp 1 - ( pos 5 , len 71 )
<div>
<div>12</div>
<div>34</div>
</div>
** Grp 2 - NULL
** Grp 3 - NULL
---------------------------
** Grp 0 - ( pos 84 , len 13 )
<div>56</div>
** Grp 1 - ( pos 89 , len 2 )
56
** Grp 2 - NULL
** Grp 3 - NULL