scala - How to choose the output collection type in Seq.map? -


i'd implement like:

def f(s: seq[int]): vector[string] = s.map(_.tostring).tovector

but i'd create directly output vector without executing map first, making whatever seq, before copying vector.

seq.map takes implicit canbuilfrom parameters induces collection output type. tried s.map(...)(vector.canbuildfrom[string]) gives error:

 found   : scala.collection.generic.canbuildfrom[vector.coll,string,scala.collection.immutable.vector[string]] (which expands to)  scala.collection.generic.canbuildfrom[scala.collection.immutable.vector[_],string,scala.collection.immutable.vector[string]]  required: scala.collection.generic.canbuildfrom[seq[int],string,vector[string]]        def f(s: seq[int]): vector[string] = s.map(_.tostring)(vector.canbuildfrom[string])

basically doesn't infer correctly first type argument of canbuildfrom

how can done ?

breakout you're looking for

def f(s: seq[int]): vector[string] = s.map(_.tostring)(collection.breakout)

for in-depth discussion of breakout does, check out stackoverflow question: scala 2.8 breakout


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