GO by example, part 5

5-go-by-example/46-collection-function.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+)
+
+// in Go it’s common to provide collection functions if and when they are specifically needed for your program and data types
+
+// Index returns the first index of the target string t, or -1 if no match is found
+func Index(vs []string, t string) int {
+	for i, v := range vs {
+		if v == t {
+			return i
+		}
+	}
+	return -1
+}
+
+// Include returns true if the target string t is in the slice
+func Include(vs []string, t string) bool {
+	return Index(vs, t) >= 0
+}
+
+// Any returns true if one of the strings in the slice satisfies the predicate f
+func Any(vs []string, f func(string) bool) bool {
+	for _, v := range vs {
+		if f(v) {
+			return true
+		}
+	}
+	return false
+}
+
+// All returns true if all of the strings in the slice satisfy the predicate f
+func All(vs []string, f func(string) bool) bool {
+	for _, v := range vs {
+		if !f(v) {
+			return false
+		}
+	}
+	return true
+}
+
+// Filter returns a new slice containing all strings in the slice that satisfy the predicate f
+func Filter(vs []string, f func(string) bool) []string {
+	vsf := make([]string, 0)
+	for _, v := range vs {
+		if f(v) {
+			vsf = append(vsf, v)
+		}
+	}
+	return vsf
+}
+
+// Map returns a new slice containing the results of applying the function f to each string in the original slice
+func Map(vs []string, f func(string) string) []string {
+	vsm := make([]string, len(vs))
+	for i, v := range vs {
+		vsm[i] = f(v)
+	}
+	return vsm
+}
+
+func main() {
+	// try out various collection functions
+	var strs = []string{"peach", "apple", "pear", "plum"}
+
+	fmt.Println(Index(strs, "pear"))
+
+	fmt.Println(Include(strs, "grape"))
+
+	fmt.Println(Any(strs, func(v string) bool {
+		return strings.HasPrefix(v, "p")
+	}))
+
+	fmt.Println(All(strs, func(v string) bool {
+		return strings.HasPrefix(v, "p")
+	}))
+
+	fmt.Println(Filter(strs, func(v string) bool {
+		return strings.Contains(v, "e")
+	}))
+
+	fmt.Println(Map(strs, strings.ToUpper))
+
+}