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delexi/gist:4033145

Created November 7, 2012 17:39
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for expression and apply syntactic sugar
Raw
gistfile1.scala
val l = List("ab", "cd", "ef")
// Compiliert
(for(x<-l; if x.indexOf('c') >= 0) yield (l.indexOf(x), x.indexOf('c'))).apply(0)
// Compiliert nicht:
// <console>:9: error: type mismatch;
// found : Int(0)
// required: scala.collection.generic.CanBuildFrom[List[java.lang.String],(Int, Int),?]
// (for(x<-l; if x.indexOf('c') >= 0) yield (l.indexOf(x), x.indexOf('c')))(0)
(for(x<-l; if x.indexOf('c') >= 0) yield (l.indexOf(x), x.indexOf('c')))(0)
@kiritsuku
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kiritsuku commented Nov 7, 2012

Does not work because the for-expression is translated to a combination of higher order functions (map, flatMap, filterWith). All of these methods have a second parameter list expecting a CanBuildFrom and by writing xs.map(f)(0) this second parameter list is called instead of apply.

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