A simple example of filter, map, reduce method

filter-map-reduce.swift

/*
 Filter
 */
let familyNames = ["Park", "Lee", "Jong", "Kim", "Choi"]
let longFamilyNames = familyNames.filter { $0.count > 3 }
print(longFamilyNames)
// ["Park", "Jong", "Choi"]


let familyNames = ["Park", "Lee", "Jong", "Kim", "Choi"]
var longFamilyNames = [String]()
for familyName in familyNames {
    if familyName.count > 3 {
        longFamilyNames.append(familyName)
    }
}
print(longFamilyNames)
// ["Park", "Jong", "Choi"]


/*
 Map
 */
let prices: [Double] = [400, 350, 150, 225, 500]
let totalPricesWithTax = prices.map { $0 * 1.05 }
print(totalPricesWithTax)
// [420.0, 367.5, 157.5, 236.25, 525.0]


let prices: [Double] = [400, 350, 150, 225, 500]
var totalPricesWithTax = [Double]()
for price in prices {
    totalPricesWithTax.append(price * 1.05)
}
print(totalPricesWithTax)
// [420.0, 367.5, 157.5, 236.25, 525.0]

/*
 Reduce
 */
let prices: [Double] = [420.0, 367.5, 157.5, 236.25, 525.0]
let totalPrice = prices.reduce(0.0, +)
print(totalPrice)
// 1706.25


let prices: [Double] = [420.0, 367.5, 157.5, 236.25, 525.0]
var totalPrice: Double = 0
for price in prices {
    totalPrice += price
}
print(totalPrice)
// 1706.25

let numbers = [1, 2, 3, 4]
let numberSum = numbers.reduce(0) { x, y in x + y }
print(numberSum)
// 10