Add string_length.

src/clojush.clj

@@ -970,6 +970,14 @@ boolean stack."
                                   (pop-item :string (pop-item :integer state)))
                        state)))
 
+(define-registered string_length
+                   (fn [state]
+                     (if (not (empty? (:string state)))
+                       (push-item (count (stack-ref :string 0 state))
+                                  :integer
+                                  (pop-item :string state))
+                       state)))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; code and exec instructions
 

src/examples/string.clj

@@ -23,3 +23,10 @@
 
 ; Add string_concat to this example, and make the number of unique characters higher. Maybe only use
 ; upper case, and try to evolve a string with all 26 letters.
+
+
+
+; New GP problem: Take the input string, remove the last 2 characters, and then concat this result with itself.
+; The fitness will be the number of non-matching characters in the resulting string. For example,
+; desired result of "abcde" would be "abcabc", and a string of "abcabcrrr" would have an error of 3, for
+; 3 too many characters, and the string "aaaaaa" would have error of 4, since it gets 2 of the characters right.

src/string_tests.clj

@@ -8,9 +8,12 @@
 
 
 ; Test strings inserted into code
-(println (run-push '(string_rand "these" "are" "strings" string_concat)
+#_(println (run-push '(string_rand "these" "are" "strings" string_concat)
                    (make-push-state)  false false))
 
 
-(println (run-push '("abcde" "HelloWorld" 7 string_take)
+#_(println (run-push '("abcde" "HelloWorld" 7 string_take)
+                   (make-push-state)))
+
+#_(println (run-push '("d2" string_length)
                    (make-push-state)))