Scala regex match and split

Question

So here's what I want to do:

input string: "abc From: blah" I want to split this so that the result is

["abc" "From: blah"] or ["abc" "From" "blah"

I have several other patterns to match ["abcd" "To:" "blah"] etc

So I have the following regex

val datePattern = """((.*>.*)|(.*(On).*(wrote:)$)|(.*(Date):.*(\+\d\d\d\d)?$)|(.*(From):.*(\.com)?(\]|>)?$))"""
val reg = datePattern.r

If I do a match the result comes out fine. If I do a split on the same regex I get an empty list.

inputStr match {
      case reg(_*) => return "Match"
      case _ => return "Output: None"
}

on the input string :

"abc From: blah blah"

returns Match

Split

inputStr.split(datePattern)

returns an empty array. What am I possibly missing ?

You cannot have one and the same regex to match and to split a string, unless you expect to get different results. — Wiktor Stribiżew, Dec 03 '15 at 14:18
Sorry didn't quite get that. So the split regex has to be different ? I tried just doing the split without the match - even then the split failed. Scala noob here. — Pradeep Banavara, Dec 03 '15 at 14:20
I think you can do that with [`"abc From: blah".split("\\W+")`](http://ideone.com/LpzvGm). — Wiktor Stribiżew, Dec 03 '15 at 14:40

score 1 · Accepted Answer · edited May 23 '17 at 10:27

1

Since the regexp matches the string, split will remove the entire string (considered as a separator).
The default behavior is not to return two empty strings, but an empty array in this case, as given by the split signification.

https://stackoverflow.com/a/14602089/1287856

Concerning why your regex matches in its entirety, you might find this website useful (it concerns your example directly)

https://regex101.com/r/zY0lX9/1

Split finds the whole regexp and removes all its occurences from the string, returning the interleaved strings as an array. You may want to split on something like "(?=From:)" so that it does not remove anything.

edited May 23 '17 at 10:27

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answered Dec 03 '15 at 15:12

Mikaël Mayer

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Thank you. That was very helpful. I'm still a bit stumped as to why "abc From: def" is matched in it's entirety. I'm expecting on the 'From:' substring to match as evidenced by the regex. So shouldn't I get "abc" "From: def" or something like that upon splitting ? – Pradeep Banavara Dec 03 '15 at 15:33

Scala regex match and split

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