add list? function to hy.core

`list?` will test if the argument is an instance of list.

NEWS.rst

@@ -11,6 +11,7 @@ New Features
 ------------------------------
 * Format strings with embedded Hy code (e.g., `f"The sum is {(+ x y)}"`)
   are now supported, even on Pythons earlier than 3.6.
+* New list? function.
 
 Bug Fixes
 ------------------------------

docs/language/core.rst

@@ -899,6 +899,24 @@ Returns the first logically-true value of ``(pred x)`` for any ``x`` in
    True
 
 
+.. _list?-fn:
+
+list?
+-----
+
+Usage: ``(list? x)``
+
+Returns ``True`` if *x* is a list.
+
+.. code-block:: hy
+
+   => (list? '(inc 41))
+   True
+
+   => (list? '42)
+   False
+
+
 .. _string?-fn:
 
 string?

hy/core/language.hy

@@ -203,6 +203,9 @@ Return series of accumulated sums (or other binary function results)."
   "Check if x is float."
   (isinstance x float))
 
+(defn list? [x]
+  (isinstance x list))
+
 (defn symbol? [s]
   "Check if `s` is a symbol."
   (instance? HySymbol s))
@@ -454,7 +457,7 @@ Even objects with the __name__ magic will work."
     disassemble drop drop-last drop-while empty? eval even? every? exec first
     filter flatten float? fraction gensym group-by identity inc input instance?
     integer integer? integer-char? interleave interpose islice iterable?
-    iterate iterator? juxt keyword keyword? last macroexpand
+    iterate iterator? juxt keyword keyword? last list? macroexpand
     macroexpand-1 mangle map merge-with multicombinations name neg? none? nth
     numeric? odd? partition permutations pos? product range read read-str
     remove repeat repeatedly rest reduce second some string string? symbol?

tests/native_tests/core.hy

@@ -267,6 +267,11 @@ result['y in globals'] = 'y' in globals()")
   (assert-true (symbol? 'im-symbol))
   (assert-false (symbol? (name 'im-symbol))))
 
+(defn test-list? []
+  "NATIVE: testing the list? function"
+  (assert-false (list? "hello"))
+  (assert-true (list? [1 2 3])))
+
 (defn test-gensym []
   "NATIVE: testing the gensym function"
   (import [hy.models [HySymbol]])