Initial data commit

Task/Substring/Racket/substring.rkt

@@ -0,0 +1,25 @@
+#lang racket
+
+(define str "abcdefghijklmnopqrstuvwxyz")
+
+(define n 10)
+(define m 2)
+(define start-char #\x)
+(define start-str "xy")
+
+;; starting from n characters in and of m length;
+(substring str n (+ n m)) ; -> "kl"
+
+;; starting from n characters in, up to the end of the string;
+(substring str m) ; -> "klmnopqrstuvwxyz"
+
+;; whole string minus last character;
+(substring str 0 (sub1 (string-length str))) ; -> "abcdefghijklmnopqrstuvwxy"
+
+;; starting from a known character within the string and of m length;
+(substring str (caar (regexp-match-positions (regexp-quote (string start-char))
+                                             str))) ; -> "xyz"
+
+;; starting from a known substring within the string and of m length.
+(substring str (caar (regexp-match-positions (regexp-quote start-str)
+                                             str))) ; -> "xyz"