merge #547 - keyword?

hy/core/language.hy

@@ -44,6 +44,11 @@
   "Check whether c can be used as a cons object"
   (instance? HyCons c))
 
+(defn keyword? [k]
+  "Check whether k is a keyword"
+  (and (instance? (type :foo) k)
+       (.startswith k (get :foo 0))))
+
 (defn cycle [coll]
   "Yield an infinite repetition of the items in coll"
   (setv seen [])
@@ -354,7 +359,7 @@
 (def *exports* '[calling-module-name coll? cons cons? cycle dec distinct
                  disassemble drop drop-while empty? even? every? first filter
                  flatten float? gensym identity inc instance? integer
-                 integer? integer-char? iterable? iterate iterator?
+                 integer? integer-char? iterable? iterate iterator? keyword?
                  list* macroexpand macroexpand-1 neg? nil? none? nth
                  numeric? odd? pos? remove repeat repeatedly rest second
                  some string string? take take-nth take-while zero? zipwith])

tests/native_tests/core.hy

@@ -478,3 +478,14 @@
   (assert-equal (list res) [4 4 4])
   (setv res (zipwith operator.sub [3 7 9] [1 2 4]))
   (assert-equal (list res) [2 5 5]))
+
+(defn test-is-keyword []
+  "NATIVE: testing the keyword? function"
+  (assert (keyword? ':bar))
+  (assert (keyword? ':baz))
+  (assert (keyword? :bar))
+  (assert (keyword? :baz))
+  (assert (not (keyword? "foo")))
+  (assert (not (keyword? ":foo")))
+  (assert (not (keyword? 1)))
+  (assert (not (keyword? nil))))