Include the splitting pattern/token from scala regex.split()

Question

The scala.util.matching.Regex appears to only have a single split() method whose behavior is to extract the match and return only the non-matching segments of the input string:

val str = "Here is some stuff PAT and second token PAT and third token PAT and fourth"
val r = "PAT".r
r.split(str)

res14: Array[String] = Array("Here is some stuff ", " and second token ", "
and third token ", " and fourth")

So is there another approach commonly used to retain the tokens in the returned list?

Note: the splitting patterns I use for actual work are somewhat complicated and certainly not constants like the above example. Therefore, simply inserting alternating constant values (or zipping them) would not suffice.

Update Here is a more representative regex

val str = "Here is some stuff PAT and second token PAT and third token 
           or something else and fourth"
val r = "(PAT|something else)".r
r.split(str)

res14: Array[String] = Array("Here is some stuff ", " and second token ", "
and third token ", " and fourth")

How complicated is the pattern? If it is not, then a mere val r = "((?<=PAT)|(?=PAT))".r could help. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 22, 2015 at 20:22
@stribizhev Well I need to put character classes in there. Your comment is already interesting (so pls add as answer) . I am checking if it were actually sufficient to completely satisfy the need. — WestCoastProjects
– WestCoastProjects, Commented Nov 22, 2015 at 20:31
@stribizhev I updated the OP. Your suggestion DOES work - even for the expanded scope. Please create an answer - and maybe add a little explanation with it. — WestCoastProjects
– WestCoastProjects, Commented Nov 22, 2015 at 20:32

Wiktor Stribiżew · Accepted Answer · 2015-11-22 20:39:01Z

For a non-complicated pattern that does not involve patterns of indefinite width, you can use a lookbehind/lookahead solution:

val str = "Here is some stuff PAT and second token PAT and third token PAT and fourth"
val r = "((?<=PAT)|(?=PAT))".r
print(r.split(str).toList)

Output of the sample demo: List(Here is some stuff , PAT, and second token , PAT, and third token , PAT, and fourth)

The idea is just to match the empty strings before (?<=PAT) and after (?=PAT) the PAT pattern, and only split there. Unfortunately, there is no such a handy feature as split using a regex with a capturing group and keep the captured text as an element of the resulting array/list.

As an alternative, the matching regex with findAllIn should be used. Or temporary one-character delimiters in front or end of the delimiting pattern can be created to further split against them.

Collectives™ on Stack Overflow

Include the splitting pattern/token from scala regex.split()

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related