Implement del

Closes #385.

docs/language/api.rst

@@ -378,6 +378,39 @@ between the operands.
   => (infix (1 + 1))
   2
 
+del
+---
+
+.. versionadded:: 0.9.12
+
+`del` removes an object from the current namespace.
+
+.. code-block:: clj
+
+  => (setv foo 42)
+  => (del foo)
+  => foo
+  Traceback (most recent call last):
+    File "<console>", line 1, in <module>
+  NameError: name 'foo' is not defined
+
+`del` can also remove objects from a mapping, a list, ...
+
+.. code-block:: clj
+
+  => (setv test (list (range 10)))
+  => test
+  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+  => (del (slice test 2 4)) ;; remove items from 2 to 4 excluded
+  => test
+  [0, 1, 4, 5, 6, 7, 8, 9]
+  => (setv dic {"foo" "bar"})
+  => dic
+  {"foo": "bar"}
+  => (del (get dic "foo"))
+  => dic
+  {}
+
 eval
 ----
 

hy/compiler.py

@@ -1099,6 +1099,21 @@ class HyASTCompiler(object):
             slice=ast.Index(value=sli.force_expr),
             ctx=ast.Load())
 
+    @builds("del")
+    @checkargs(min=1)
+    def compile_del_expression(self, expr):
+        expr.pop(0)
+        ld_targets, ret = self._compile_collect(expr)
+
+        del_targets = []
+        for target in ld_targets:
+            del_targets.append(self._storeize(target, ast.Del))
+
+        return ret + ast.Delete(
+            lineno=expr.start_line,
+            col_offset=expr.start_column,
+            targets=del_targets)
+
     @builds("slice")
     @checkargs(min=1, max=4)
     def compile_slice_expression(self, expr):

tests/native_tests/language.hy

@@ -789,3 +789,18 @@
   (assert (string? (string "a")))
   (assert (string? (string 1)))
   (assert (= u"unicode" (string "unicode"))))
+
+(defn test-del []
+  "NATIVE: Test the behavior of del"
+  (setv foo 42)
+  (assert (= foo 42))
+  (del foo)
+  (assert (= 'good
+    (try
+      (do foo 'bad)
+      (except [NameError] 'good))))
+  (setv test (list (range 5)))
+  (del (get test 4))
+  (assert (= test [0 1 2 3]))
+  (del (get test 2))
+  (assert (= test [0 1 3])))