strings: update

Author: changkun

strings/strings.go

@@ -4,17 +4,51 @@
 
 package strings
 
-// An interface specifies methods and types for each of the
-// type parameters it constrains.
+// Stringer is a type constraint that requires the type argument to have
+// a String method and permits the generic function to call String.
+// The String method should return a string reqpresentation of the value.
 type Stringer interface {
 	String() string
 }
 
-
-func Stringify[type T Stringer](s []T) ([]string) {
-	ret := []string{}
+// Stringify calls the String method on each element of s,
+// and returns the results.
+func Stringify[type T Stringer](s []T) (ret []string) {
 	for _, v := range s {
 		ret = append(ret, v.String())
 	}
-	return ret
+	return
+}
+
+// Stringify2 converts two slices of different types to strings,
+// and returns the concatenation of all the strings.
+func Stringify2[type T1, T2 Stringer](s1 []T1, s2 []T2) string {
+	r := ""
+	for _, v1 := range s1 {
+		r += v1.String()
+	}
+	for _, v2 := range s2 {
+		r += v2.String()
+	}
+	return r
+}
+
+// Plusser is a type constraint that requires a Plus method.
+// The Plus method is expected to add the argument to an internal
+// string and return the result.
+type Plusser interface {
+	Plus(string) string
+}
+
+// ConcatTo takes a slice of elements with a String method and a slice
+// of elements with a Plus method. The slices should have the same
+// number of elements. This will convert each element of s to a string,
+// pass it to the Plus method of the corresponding element of p,
+// and return a slice of the resulting strings.
+func ConcatTo[type S Stringer, P Plusser](s []S, p []P) []string {
+	r := make([]string, len(s))
+	for i, v := range s {
+		r[i] = p[i].Plus(v.String())
+	}
+	return r
 }