Data commit

Task/Increment-a-numerical-string/TXR/increment-a-numerical-string-1.txr

@@ -0,0 +1,11 @@
+@(do (defun inc-num-str (str-in)
+       (let ((len (length str-in))
+             (str (copy-str str-in)))
+         (for ((i (- len 1)))
+              ((>= i 0) `1@str`)
+              ((dec i))
+           (if (<= (inc [str i]) #\9)
+             (return str)
+             (set [str i] #\0))))))
+@(bind a @(inc-num-str "9999"))
+@(bind b @(inc-num-str "1234"))

Task/Increment-a-numerical-string/TXR/increment-a-numerical-string-2.txr

@@ -0,0 +1,21 @@
+@(deffilter incdig ("0" "1") ("1" "2") ("2" "3") ("3" "4") ("4" "5")
+                   ("5" "6") ("6" "7") ("7" "8") ("8" "9"))
+@(define increment (num out))
+@  (local prefix dig junk)
+@  (next :string num)
+@  (cases)
+9
+@    (bind out "10")
+@  (or)
+@*{prefix}@{dig /[0-8]/}
+@    (bind out `@prefix@{dig :filter incdig}`)
+@  (or)
+@*{prefix}9
+@    (bind out `@{prefix :filter (:fun increment)}0`)
+@  (or)
+@junk
+@    (throw error `bad input: @junk`)
+@  (end)
+@(end)
+@in
+@(increment in out)