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Higher Order Functions better explanations #84

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May 19, 2017
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17 changes: 11 additions & 6 deletions src/main/scala/stdlib/HigherOrderFunctions.scala
Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,10 @@ object HigherOrderFunctions
result2 should be(res1)
}

/** We can take that closure and throw it into a method and it will still hold the environment:
/** And then we get to Higher Order Functions:
* Higher Order Functions are functions that take functions as arguments and/or return functions.
*
* We can take that closure and throw it into a Higher Order Function and it will still hold the environment:
*/
def holdEnvironmentHigherOrderFunctions(res0: Int, res1: Int) {
def summation(x: Int, y: Int ⇒ Int) = y(x)
Expand All @@ -102,7 +105,7 @@ object HigherOrderFunctions
result2 should be(res1)
}

/** Function returning another function:
/** Higher Order Function returning another function:
*/
def returningFunctionHigherOrderFunctions(res0: Boolean, res1: Int, res2: Int) {
def addWithoutSyntaxSugar(x: Int): Function1[Int, Int] = {
Expand Down Expand Up @@ -145,7 +148,8 @@ object HigherOrderFunctions
def functionAsParameterHigherOrderFunctions(
res0: List[String],
res1: List[String],
res2: List[Int]) {
res2: List[String],
res3: List[Int]) {
def makeUpper(xs: List[String]) = xs map {
_.toUpperCase
}
Expand All @@ -160,9 +164,10 @@ object HigherOrderFunctions
}) should be(res1)

//using it inline
List("Scala", "Erlang", "Clojure") map {
_.length
} should be(res2)
val myName = (name: String) => s"My name is $name"
makeWhatEverYouLike(List("John", "Mark"), myName) should be(res2)

List("Scala", "Erlang", "Clojure") map (_.length) should be(res3)
}

}
3 changes: 2 additions & 1 deletion src/test/scala/stdlib/HigherOrderFunctionsSpec.scala
Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,8 @@ class HigherOrderFunctionsSpec extends Spec with Checkers {
Test
.testSuccess(
HigherOrderFunctions.functionAsParameterHigherOrderFunctions _,
List("ABC", "XYZ", "123") :: List("abc", "xyz", "123") :: List(5, 6, 7) :: HNil
List("ABC", "XYZ", "123") :: List("abc", "xyz", "123") ::
List("My name is John", "My name is Mark") :: List(5, 6, 7) :: HNil
)
)
}
Expand Down