Add shadow.hy to core

This new core module allows us to shadow the builtin Python operators so
they may be passed to sequence functions that expect functions:

    => (map / [1 2 3 4 5])
    [1.0, 0.5, 0.3333333333333333, 0.25]

hy/core/__init__.py

@@ -1,3 +1,4 @@
 STDLIB = [
-    "hy.core.language"
+    "hy.core.language",
+    "hy.core.shadow"
 ]

hy/core/language.hy

@@ -92,7 +92,8 @@
     (setv map itertools.imap)
     (setv zip itertools.izip)
     (setv range xrange)
-    (setv input raw_input))
+    (setv input raw_input)
+    (setv reduce reduce))
   (do
     (setv reduce functools.reduce)
     (setv filterfalse itertools.filterfalse)
@@ -331,10 +332,12 @@
   (_numeric_check n)
   (= n 0))
 
-(def *exports* '[butlast 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? keyword?
-                 list* macroexpand macroexpand-1 map neg? nil? none? nth
-                 numeric? odd? pos? range remove repeat repeatedly rest second
-                 some string string? take take-nth take-while zero? zip zipwith])
+(def *exports* '[butlast 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? keyword? list*
+                 macroexpand macroexpand-1 map neg? nil? none? nth
+                 numeric? odd? pos? range remove repeat repeatedly
+                 rest reduce second some string string? take take-nth
+                 take-while zero? zip zipwith])

hy/core/shadow.hy

@@ -0,0 +1,61 @@
+;; Copyright (c) 2014 Paul Tagliamonte <paultag@debian.org>
+;; Copyright (c) 2014 James King <james@agentultra.com>
+
+;; Permission is hereby granted, free of charge, to any person obtaining a
+;; copy of this software and associated documentation files (the "Software"),
+;; to deal in the Software without restriction, including without limitation
+;; the rights to use, copy, modify, merge, publish, distribute, sublicense,
+;; and/or sell copies of the Software, and to permit persons to whom the
+;; Software is furnished to do so, subject to the following conditions:
+
+;; The above copyright notice and this permission notice shall be included in
+;; all copies or substantial portions of the Software.
+
+;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+;; THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+;; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+;; DEALINGS IN THE SOFTWARE.
+
+;;;; Hy shadow functions
+
+(import operator)
+
+
+(defn + [&rest args]
+  "Shadow + operator for when we need to import / map it against something"
+  (if (= (len args) 0)
+    0
+    (sum args)))  ; shortcut here.
+
+
+(defn - [&rest args]
+  "Shadow - operator for when we need to import / map it against something"
+  (let [[count (len args)]]
+    (if (= count 0)
+      (raise (TypeError "Need at least 1 argument to subtract"))
+      (if (= count 1)
+        (- (get args 0))
+        (reduce operator.sub args)))))
+
+
+(defn * [&rest args]
+  "Shadow * operator for when we need to import / map it against something"
+  (if (= (len args) 0)
+    1  ; identity
+    (reduce operator.mul args)))
+
+
+(defn / [&rest args]
+  "Shadow / operator for when we need to import / map it against something"
+  (let [[count (len args)]]
+    (if (= count 0)
+      (raise (TypeError "Need at least 1 argument to divide"))
+      (if (= count 1)
+        (operator.truediv 1 (get args 0))
+        (reduce operator.truediv args)))))
+
+
+(setv *exports* ['+ '- '* '/])

tests/native_tests/shadow.hy

@@ -0,0 +1,41 @@
+
+
+(defn test-shadow-addition []
+  "NATIVE: test shadow addition"
+  (let [[x +]]
+    (assert (= (x) 0))
+    (assert (= (x 1 2 3 4) 10))
+    (assert (= (x 1 2 3 4 5) 15))))
+
+
+(defn test-shadow-subtraction []
+  "NATIVE: test shadow subtraction"
+  (let [[x -]]
+    (assert (try
+             (x)
+             (catch [TypeError] True)
+             (else (throw AssertionError))))
+    (assert (= (x 1) -1))
+    (assert (= (x 2 1) 1))
+    (assert (= (x 2 1 1) 0))))
+
+
+(defn test-shadow-multiplication []
+  "NATIVE: test shadow multiplication"
+  (let [[x *]]
+    (assert (= (x) 1))
+    (assert (= (x 3) 3))
+    (assert (= (x 3 3) 9))))
+
+
+(defn test-shadow-division []
+  "NATIVE: test shadow division"
+  (let [[x /]]
+    (assert (try
+             (x)
+             (catch [TypeError] True)
+             (else (throw AssertionError))))
+    (assert (= (x 1) 1))
+    (assert (= (x 8 2) 4))
+    (assert (= (x 8 2 2) 2))
+    (assert (= (x 8 2 2 2) 1))))