added docker image

functions/iterables.go

@@ -0,0 +1,18 @@
+package functions
+
+func MapArrayInsert[K comparable, V any](m map[K][]V, k K, v V) {
+	l, ok := m[k]
+	if !ok {
+		m[k] = []V{v}
+	} else {
+		m[k] = append(l, v)
+	}
+}
+
+func Keys[K comparable, V any](m map[K]V) []K {
+	keys := make([]K, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	return keys
+}