--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libutil/extdigits.c	Sun Jun 26 23:35:19 2022 -0800
@@ -0,0 +1,29 @@
+/*
+ * The library function implemented in this module checks "extended"
+ * number digits, i.e., checks whether or not a given character
+ * makes a valid "extended" number digit.
+ */
+
+is_valid_ext_digit(c)
+{
+	switch (c) {
+	case '0':
+	case '1':
+	case '2':
+	case '3':
+	case '4':
+	case '5':
+	case '6':
+	case '7':
+	case '8':
+	case '9':
+	case '*':
+	case '#':
+	case 'a':
+	case 'b':
+	case 'c':
+		return(1);
+	default:
+		return(0);
+	}
+}