Regular expressions - does Scala not have modifiers? If so ... why?

[Brent Gracey]

Hi all; 

I'm having a look at Regular Expression in scala - and wondering if I'm missing what the equivalent of 'modifiers' (from PHP  or Java) are?

From https://regex101.com/#pcre it gives a Modifier quick reference (top right) based on the Flavor selected; top middle on the Left.

My googleing turned up

http://stackoverflow.com/questions/17930774/scala-regex-ignorecase
where the (?i) enables case insensitive matching

http://stackoverflow.com/questions/1088554/scala-regex-enable-multiline-option
(?s) is key here in regard to matching against multi-line strings


But the PHP and Java (my understanding is  http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html#Field Detail is relatively equivalent) modifiers seem to be a longer list.

So after that pre-amble

1) Am I correct in my understanding that Scala Regex doesn't have a suite of modifiers?
2) If so; is there a reason for this? Are modifiers just 'syntax sugar' that can be implemented in Regex expressions without using special cases?


Thanks

[Simon Ochsenreither]

Scala regexes are basically Java regexes. Everything which is supported on the Java version you are running, also works in Scala.

[Som Snytt]

It's a weakness of the JavaDoc that it's difficult to correlate the inline flags with the flags argument.

(?idmsuxU-idmsuxU) are inline flags.

A couple of flag arg values have no inline option:

http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html#CANON_EQ

The Scala API doesn't accommodate the flag args. I don't know if there's a great reason for that.

scala> :pa -raw
// Entering paste mode (ctrl-D to finish)

package scala.util.matching { object X { def x(p: java.util.regex.Pattern) = new Regex(p) } }

// Exiting paste mode, now interpreting.


scala> val r = util.matching.X.x(Pattern.compile("abc", Pattern.CASE_INSENSITIVE))
r: scala.util.matching.Regex = abc

scala> "ABC" match { case r(_*) => }

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[Brent Gracey]

Hi -

Thanks for the pointers that I am actually pretty close to the Java libraries; that should help me going forward.

I tried the below in the repl and got

scala> :pa -raw
// Entering paste mode (ctrl-D to finish)


package scala.util.matching { object X { def x(p: java.util.regex.Pattern) = new Regex(p) } }


// Exiting paste mode, now interpreting.

<console>:1: error: illegal start of definition
       package scala.util.matching { object X { def x(p: java.util.regex.Pattern) = new Regex(p) } }
       ^

And in my code I gave

package utils
import java.util.regex.Pattern
import scala.util.matching.Regex


object RegexHelper {

 def applyThat(regexExp: String, context: String) = {

 val myPattern: Pattern = java.util.regex.Pattern.compile("abc", java.util.regex.Pattern.CASE_INSENSITIVE)
 val r = X.x(myPattern)

 "ABC" match { case r(_*) => }

 }
}

object X { def x(p: java.util.regex.Pattern) = new Regex(p) }

Which gives a compile error

type mismatch;
 found : java.util.regex.Pattern
 required: String

object X { def x(p: java.util.regex.Pattern) = new Regex(p) }

Which I think has to do with not being in the correct namespace for my object X definition?

[Som Snytt]

Looks like you're using a scala version from a time long, long ago.

Try 2.11, if you can, to exploit the library internals.

I'm going to update my scala script to set the prompt to include the version...

[Brent Gracey]

Ah; thanks for helping me through; I am indeed on a slightly historic version of our fav language.