Add inc/dec

Close #275

src/clj.lfe

@@ -628,6 +628,13 @@
   N.B. This is like Haskell's `const` rather than Clojure's `constantly`."
   (lambda (_) x))
 
+(defn inc [x]
+  "Increment `x` by 1."
+  (+ x 1))
+
+(defn dec [x]
+  "Decrement `x` by 1."
+  (- x 1))
 
 ;;; Internal functions.
 

test/clj-tests.lfe

@@ -611,7 +611,7 @@
   (is-error 'function_clause (clj:repeat -1 0))
   (is-error 'function_clause (clj:repeat -1 (lambda () 1))))
 
-;;; identity and constantly
+;;; Other functions.
 
 (deftest identity
   (are* [x] (ok? (is-match x (clj:identity x)))
@@ -634,4 +634,12 @@
     (are* [x] (ok? (is-match 10 (c0 x)))
           'nil
           42
-          "foo")))
+          "foo")))
+
+(deftest inc
+  (is-match 2 (clj:inc 1))
+  (is-match 4.0 (clj:inc 3.0)))
+
+(deftest dec
+  (is-match 2 (clj:dec 3))
+  (is-match 4.0 (clj:dec 5.0)))