Add int-string? to check if a string is a number.

src/cipher_analytical_machine/parsers/parsers.clj

@@ -8,6 +8,12 @@
   (if (re-matches #"\d+" str)
     true false))
 
+(defn int-string?
+  "Return true if the string is an signed integer."
+  [str]
+  (if (re-matches #"[+-]?\b\d+\b" str)
+    true false))
+
 (defn parse-unsigned-int
   "Return an integer if the argument is an integer."
   [str-or-int]