98 lines
2.1 KiB
Go
98 lines
2.1 KiB
Go
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// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import (
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"fmt"
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)
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type filterFunc func(int) bool
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func main() {
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fmt.Println("••• HIGHER-ORDER FUNCS •••")
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nums := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
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odd := reverse(reverse(isEven))
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fmt.Printf("reversed : %t\n", odd(8))
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fmt.Printf("> 3 : %d\n", filter(greater(3), nums...))
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fmt.Printf("> 6 : %d\n", filter(greater(6), nums...))
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fmt.Printf("<= 6 : %d\n", filter(lesseq(6), nums...))
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fmt.Printf("<= 6 : %d\n", filter(reverse(greater(6)), nums...))
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fmt.Println("\n••• CLOSURES •••")
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fmt.Printf("uniques : %d\n", filter(uniques(), 1, 1, 2, 3, 3))
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dups := reverse(uniques())
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fmt.Printf("dups : %v\n", filter(dups, 1, 1, 2, 3, 3))
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dups = reverse(uniques())
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fmt.Printf("dups dups : %v\n", filter(dups, 1, 1, 2, 3, 3, 3, 3))
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dups = reverse(uniques())
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out := filter(dups, 1, 1, 2, 3, 3, 3, 3)
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fmt.Printf("dups uniqs : %v\n", filter(uniques(), out...))
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dups = reverse(uniques())
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chained := chain(reverse(greater(1)), dups, uniques())
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fmt.Printf("dups chain : %v\n", filter(chained, 1, 1, 2, 3, 3, 3, 3, 0, 0))
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}
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func chain(filters ...filterFunc) filterFunc {
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return func(n int) bool {
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for _, next := range filters {
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if !next(n) {
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return false
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}
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}
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return true
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}
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}
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func uniques() filterFunc {
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seen := make(map[int]bool)
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return func(n int) (ok bool) {
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if !seen[n] {
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seen[n], ok = true, true
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}
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return
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}
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}
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func reverse(f filterFunc) filterFunc {
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return func(n int) bool {
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return !f(n)
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}
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}
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func greater(min int) filterFunc {
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return func(n int) bool {
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return n > min
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}
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}
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func lesseq(max int) filterFunc {
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return func(n int) bool {
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return n <= max
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}
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}
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func filter(f filterFunc, nums ...int) (filtered []int) {
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for _, n := range nums {
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if f(n) {
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filtered = append(filtered, n)
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}
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}
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return
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}
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func isEven(n int) bool { return n%2 == 0 }
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func isOdd(m int) bool { return m%2 == 1 }
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