Scala Regex Pattern Matching -


i need use regex match pattern in scala , have regex 

inputpattern: scala.util.matching.regex = put (.*) in (.*)

when run follwing happens:

scala> val inputpattern(verb, item, prep, obj) = "put in b"; scala.matcherror: put in b (of class java.lang.string) ... 33 elided

i end verb("put"), item("a"), prep("in"), , obj("b") input "put in b" , verb("put"), item(""), prep("in"), , obj("") input "put in".

thanks

this works special cases :

scala> val inputpattern = "(put) (.*?) ?(in) ?(.*?)".r inputpattern: scala.util.matching.regex = (put) (.*) ?(in) ?(.*)  scala> val inputpattern(verb, item, prep, obj) = "put in b" verb: string = put item: string = prep: string = in obj: string = b  scala> val inputpattern(verb, item, prep, obj) = "put in" verb: string = put item: string = "" prep: string = in obj: string = ""

put , in here captured in groups participate in pattern matching. used lazy regexps (.*?) capture less possible, may replace (\s*). ? gives optional space match "put in" (with 1 space between put , in , no space @ end).

but aware of this:

scala> val inputpattern(verb, item, prep, obj) = "put ainb" verb: string = put item: string = prep: string = in obj: string = b  scala> val inputpattern(verb, item, prep, obj) = "put aininb" verb: string = put item: string = prep: string = in obj: string = inb  scala> val inputpattern(verb, item, prep, obj) = "put ain" verb: string = put item: string = prep: string = in obj: string = ""

if have simple command interpreter may good, otherwise should match special cases separately.

to process simple (not natural) language, may consider standardtokenparsers, context-free (chomsky type 2):

import scala.util.parsing.combinator.syntactical._  val p = new standardtokenparsers {    lexical.reserved ++= list("put", "in")     def p = "put" ~ opt(ident) ~ "in" ~ opt(ident) }  scala> p.p(new p.lexical.scanner("put in b")) warning: there 1 feature warning; re-run -feature details res13 = [1.11] parsed: (((put~some(a))~in)~some(b))  scala> p.p(new p.lexical.scanner("put in")) warning: there 1 feature warning; re-run -feature details res14 = [1.7] parsed: (((put~none)~in)~none)

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