feat(utils):增加一些常用的函数式功能。

utils/functional.go

@@ -0,0 +1,27 @@
+package utils
+
+func Map[S, T any](source []S, f func(S) T) []T {
+	dest := make([]T, len(source))
+	for i, elem := range source {
+		dest[i] = f(elem)
+	}
+	return dest
+}
+
+func Reduce[S, T any](source []S, initialValue T, f func(T, S) T) T {
+	acc := initialValue
+	for _, elem := range source {
+		acc = f(acc, elem)
+	}
+	return acc
+}
+
+func Filter[T any](source []T, f func(T) bool) []T {
+	var dest []T
+	for _, elem := range source {
+		if f(elem) {
+			dest = append(dest, elem)
+		}
+	}
+	return dest
+}