How To Use Higher Order Functions in Scala
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The document discusses higher-order functions in Scala, which enable the passing of behavior as arguments and the return of functions from methods. It provides examples using 'filter' to select elements based on a predicate and 'map' to transform elements in a list. Additionally, it touches on various collection implementations and concepts like parallel collections and futures in the context of Scala programming.
![Example:
Filter
• Set[A]
contains
a
method
called
filter:
filter(p: A => Boolean): Set[A]
• Use
it
to
select
elements
that
comply
with
a
predicate](https://image.slidesharecdn.com/scala-higherorderfunctions-140722143400-phpapp01/85/How-To-Use-Higher-Order-Functions-in-Scala-3-320.jpg)
![Example:
Filter
val set = (-10 to 10).toSet
def isEven(i:Int) = i % 2 == 0
// Set[A].filter(p: A => Boolean): Set[A]
set.filter(i => isEven(i))
set.filter(isEven(_))
set.filter(isEven)](https://image.slidesharecdn.com/scala-higherorderfunctions-140722143400-phpapp01/85/How-To-Use-Higher-Order-Functions-in-Scala-4-320.jpg)
![Example:
Map
• List[A]
contains
a
method
called
map:
map[B](f: A => B): List[B]
• Use
it
to
transform
each
element
in
the
list
by
applying
f](https://image.slidesharecdn.com/scala-higherorderfunctions-140722143400-phpapp01/85/How-To-Use-Higher-Order-Functions-in-Scala-5-320.jpg)
How To Use Higher Order Functions in Scala
- 1. Scala: Higher Order Func2ons
- 2. Higher order func2ons • Allow behavior to be passed in as arguments • Return func2ons from method calls • Allows for more abstract constructs => more library-‐like, requiring less maintenance
- 3. Example: Filter • Set[A] contains a method called filter: filter(p: A => Boolean): Set[A] • Use it to select elements that comply with a predicate
- 4. Example: Filter val set = (-10 to 10).toSet def isEven(i:Int) = i % 2 == 0 // Set[A].filter(p: A => Boolean): Set[A] set.filter(i => isEven(i)) set.filter(isEven(_)) set.filter(isEven)
- 5. Example: Map • List[A] contains a method called map: map[B](f: A => B): List[B] • Use it to transform each element in the list by applying f
- 6. Example: Map def capitalize(s: String) = s.head.toUpper + s.tail.toLowerCase val list = List("samwise", "meriadoc", "peregrin") list.map(capitalize)
- 7. Some interes2ng examples • Collec2ons – best implementa2on depends on collec2on: recursive, itera2ve, with auxiliary mutable state. • Parallel collec2ons – interface is fundamentally the same, paralleliza2on is hidden from you. • Futures – transform the value once it's available