MPN-922: complete exercises for Functional Programming in Scala, Chapter 4 #3
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added 8 commits
April 16, 2015 15:03
Implement sequence in terms of traverse.
Implement and test map, flatMap, orElse and map2.
Either.sequence is implemented in terms of Either.traverse, so testing the former is enough to test the latter.
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| def flatMap[EE >: E, B](f: A => Either[EE, B]): Either[EE, B] = | ||
| map(f) match { |
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This could be simplified by not going through map first.
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It's usually easier to implement map through flatMap than the other way around. In this case:
def map[B](f: A => B): Either[E, B] = flatMap(a => Right(f(a)))
Or flatMap(f andThen Right.apply)
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Very nice. Funny thing: this is exactly what Martin Odersky talked about in his lecture on monads in the Reactive Programming course.
added 2 commits
April 17, 2015 16:36
Using @jonas suggestion: #3 (comment)
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| package fpinscala.errorhandling | |||
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| import scala.{Option => _, Either => _, Left => _, Right => _, _} // hide std library `Option` and `Either`, since we are writing our own in this chapter | |||
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@yawaramin looks good - my+1 is conditional on @gpoirier 's though, as he has open question(s) |
yawaramin
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Apr 21, 2015
MPN-922: complete exercises for Functional Programming in Scala, Chapter 4
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