Prepped Map

Author: Bob Lee

source-code/6000_functional_programming/.DS_Store

@@ -1,41 +1,51 @@
-/*:
- 
- ## Learn Swift with Bob
- ### Functional Programming
- ### Map
- 
- **Problem:** A closure is too long to pass through a function
- 
- ---
- */
-
-
-
-var values = [2.0,4.0,5.0,7.0]
-var squares: [Double] = []
-for value in values {
- squares.append(value*value)
-}
-
-
-values = [2.0,4.0,5.0,7.0]
-squares = values.map { $0 * $0 }
-// [4.0, 16.0, 25.0, 49.0]
-
 
+//: Imperative/Non-functional
+var squaredNumbers: [Double] = []
 
+var numbers = [1.0, 2.0, 3.0, 4.0, 5.0]
+for number in numbers {
+ squaredNumbers.append(number * number)
+}
 
+numbers.map { $0 * $0 } // [1, 4, 9, 16, 25]
+let cast = ["Vivien", "Marlon", "Kim", "Karl"]
+let lowercaseNames = cast.map { $0.lowercased() }
 
+func myMap(numbers: [Double], logic: (Double) -> Double) -> [Double] {
+ var result: [Double] = []
+ for number in numbers {
+ let transformedValue = logic(number)
+ result.append(transformedValue)
+ }
+ return result
+}
 
-func myMap<T, U>(_ items: [T], _ f: (T) -> U) -> [U] {
+myMap(numbers: [1, 2, 3, 4, 5]) { (number) -> Double in number * 10 }
+myMap(numbers: [1, 2, 3, 4, 5]) { $0 * 10 }
+//: Generics 
+func myMap<T, U>(_ items: [T], _ operation: (T) -> U) -> [U] {
  var result = [U]()
  for item in items {
- result.append(f(item))
+ result.append(operation(item))
  }
  return result
 }
 
+myMap([1, 2, 3, 4 , 5, 6]) { String($0 * $0) }
+//: The Purest Form
+extension Array {
+ func myMap<U>(_ operation: (Element) -> U) -> [U] {
+ var result = [U]()
+ for item in self {
+ result.append(operation(item))
+ }
+ return result
+ }
+}
+
+
+let result = Array(1...10).myMap { $0 * 10 }
+print(result)
 
-print(myMap([1, 2, 3, 4 , 5, 6]) { $0 * $0 })
 
 

source-code/6000_functional_programming/6003_map.playground/Contents.swift

@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<playground version='5.0' target-platform='ios' display-mode='raw'>
+<playground version='5.0' target-platform='ios' display-mode='rendered'>
  <timeline fileName='timeline.xctimeline'/>
 </playground>