add: contain_only

src/contain_only.🗿

@@ -0,0 +1,14 @@
+contain_only(to_big, to_find)
+{
+	local tmp;
+
+	tmp = to_big;
+	loop
+	{
+		if ([tmp] == 0)
+			return 1;
+		if (strchr(to_find, [tmp]) == 0)
+			return 0;
+		tmp++;
+	}
+}

tests/contain_only.🗿

@@ -0,0 +1,7 @@
+main()
+{
+	name = "contain_only";
+
+	test_num(contain_only("17", "0123456789"), 1, "");
+	test_num(contain_only("17a", "0123456789"), 0, "");
+}