Merge pull request #1444 from gilch/xi-tag

change xi macro to #% tag macro

NEWS

@@ -22,6 +22,8 @@ Changes from 0.13.0
    * support EDN `#_` syntax to discard the next term
    * `return` has been implemented as a special form
    * `while` loops may now contain an `else` clause, like `for` loops
+   * `xi` from `hy.extra.anaphoric` is now the `#%` tag macro
+   * `#%` works on any expression and has a new `&kwargs` parameter `%**`
 
    [ Bug Fixes ]
    * Numeric literals are no longer parsed as symbols when followed by a dot

docs/extra/anaphoric.rst

@@ -229,21 +229,37 @@ Returns a function which applies several forms in series from left to right. The
    => (op 2)
    9
 
-.. _xi
+.. _#%
 
-xi
+#%
 ==
 
-Usage ``(xi body ...)``
+Usage ``#% expr``
 
-Returns a function with parameters implicitly determined by the presence in the body of xi parameters. An xi symbol designates the ith parameter (1-based, e.g. x1, x2, x3, etc.), or all remaining parameters for xi itself. This is not a replacement for fn. The xi forms cannot be nested.
+Makes an expression into a function with an implicit ``%`` parameter list.
 
-This is similar to Clojure's anonymous function literals (``#()``).
+A ``%i`` symbol designates the (1-based) *i* th parameter (such as ``%3``).
+Only the maximum ``%i`` determines the number of ``%i`` parameters--the
+others need not appear in the expression.
+``%*`` and ``%**`` name the ``&rest`` and ``&kwargs`` parameters, respectively.
 
 .. code-block:: hy
 
-   => ((xi identity [x1 x5 [x2 x3] xi x4]) 1 2 3 4 5 6 7 8)
+    => (#%[%1 %6 42 [%2 %3] %* %4] 1 2 3 4 555 6 7 8)
-   [1, 5, [2, 3,] (6, 7, 8), 4]
+    [1, 6, 42, [2, 3], (7, 8), 4]
-   => (def add-10 (xi + 10 x1))
+    => (#% %** :foo 2)
+    {"foo": 2}
+
+When used on an s-expression,
+``#%`` is similar to Clojure's anonymous function literals--``#()``.
+
+.. code-block:: hy
+
+    => (setv add-10 #%(+ 10 %1))
     => (add-10 6)
     16
+
+``#%`` determines the parameter list by the presence of a ``%*`` or ``%**``
+symbol and by the maximum ``%i`` symbol found *anywhere* in the expression,
+so nesting of ``#%`` forms is not recommended.
+

hy/extra/anaphoric.hy

@@ -5,7 +5,6 @@
 
 ;;; These macros make writing functional programs more concise
 
-
 (defmacro ap-if [test-form then-form &optional else-form]
   `(do
      (setv it ~test-form)
@@ -112,26 +111,32 @@
   "Returns a function which is the composition of several forms."
   `(fn [var] (ap-pipe var ~@forms)))
 
-(defmacro xi [&rest body]
+(deftag % [expr]
-  "Returns a function with parameters implicitly determined by the presence in
+  "Makes an expression into a function with an implicit `%` parameter list.
-   the body of xi parameters. An xi symbol designates the ith parameter
+
-   (1-based, e.g. x1, x2, x3, etc.), or all remaining parameters for xi itself.
+   A `%i` symbol designates the (1-based) ith parameter (such as `%3`).
-   This is not a replacement for fn. The xi forms cannot be nested. "
+   Only the maximum `%i` determines the number of `%i` parameters--the
-  (setv flatbody (flatten body))
+   others need not appear in the expression.
-  `(fn [;; generate all xi symbols up to the maximum found in body
+   `%*` and `%**` name the `&rest` and `&kwargs` parameters, respectively.
-            ~@(genexpr (HySymbol (+ "x"
+
-                                    (str i)))
+   Nesting of `#%` forms is not recommended."
-                       [i (range 1
+  (setv %symbols (set-comp a
-                                 ;; find the maximum xi
+                           [a (flatten [expr])]
-                                 (inc (max (+ (list-comp (int (cut a 1))
+                           (and (symbol? a)
-                                                         [a flatbody]
+                                (.startswith a '%))))
-                                                         (and (symbol? a)
+  `(fn [;; generate all %i symbols up to the maximum found in expr
-                                                              (.startswith a 'x)
+        ~@(genexpr (HySymbol (+ "%" (str i)))
-                                                              (.isdigit (cut a 1))))
+                   [i (range 1 (-> (list-comp (int (cut a 1))
-                                              [0]))))])
+                                              [a %symbols]
-            ;; generate the &rest parameter only if 'xi is present in body
+                                              (.isdigit (cut a 1)))
-            ~@(if (in 'xi flatbody)
+                                   (or (, 0))
-                '(&rest xi)
+                                   max
-                '())]
+                                   inc))])
-     (~@body)))
+        ;; generate the &rest parameter only if '%* is present in expr
+        ~@(if (in '%* %symbols)
+              '(&rest %*))
+        ;; similarly for &kwargs and %**
+        ~@(if (in '%** %symbols)
+              '(&kwargs %**))]
+     ~expr))
 

tests/native_tests/extra/anaphoric.hy

@@ -99,28 +99,46 @@
   (assert-equal ((ap-compose (+ it 1) (* it 3)) 2) 9)
   (assert-equal ((ap-compose (list (rest it)) (len it)) [4 5 6 7]) 3))
 
-(defn test-xi []
+(defn test-tag-fn []
-  "NATIVE: testing xi forms"
+  "NATIVE: testing #%() forms"
   ;; test ordering
-  (assert-equal ((xi / x1 x2) 2 4) 0.5)
+  (assert-equal (#%(/ %1 %2) 2 4) 0.5)
-  (assert-equal ((xi / x2 x1) 2 4) 2)
+  (assert-equal (#%(/ %2 %1) 2 4) 2)
-  (assert-equal ((xi identity (, x5 x4 x3 x2 x1)) 1 2 3 4 5) (, 5 4 3 2 1))
+  (assert-equal (#%(identity (, %5 %4 %3 %2 %1)) 1 2 3 4 5) (, 5 4 3 2 1))
-  (assert-equal ((xi identity (, x1 x2 x3 x4 x5)) 1 2 3 4 5) (, 1 2 3 4 5))
+  (assert-equal (#%(identity (, %1 %2 %3 %4 %5)) 1 2 3 4 5) (, 1 2 3 4 5))
-  (assert-equal ((xi identity (, x1 x5 x2 x3 x4)) 1 2 3 4 5) (, 1 5 2 3 4))
+  (assert-equal (#%(identity (, %1 %5 %2 %3 %4)) 1 2 3 4 5) (, 1 5 2 3 4))
   ;; test &rest
-  (assert-equal ((xi sum xi) 1 2 3) 6)
+  (assert-equal (#%(sum %*) 1 2 3) 6)
-  (assert-equal ((xi identity (, x1 xi)) 10 1 2 3) (, 10 (, 1 2 3)))
+  (assert-equal (#%(identity (, %1 %*)) 10 1 2 3) (, 10 (, 1 2 3)))
   ;; no parameters
-  (assert-equal ((xi list)) [])
+  (assert-equal (#%(list)) [])
-  (assert-equal ((xi identity "Hy!")) "Hy!")
+  (assert-equal (#%(identity "Hy!")) "Hy!")
-  (assert-equal ((xi identity "xi")) "xi")
+  (assert-equal (#%(identity "%*")) "%*")
-  (assert-equal ((xi + "Hy " "world!")) "Hy world!")
+  (assert-equal (#%(+ "Hy " "world!")) "Hy world!")
   ;; test skipped parameters
-  (assert-equal ((xi identity [x3 x1]) 1 2 3) [3 1])
+  (assert-equal (#%(identity [%3 %1]) 1 2 3) [3 1])
   ;; test nesting
-  (assert-equal ((xi identity [x1 (, x2 [x3] "Hy" [xi])]) 1 2 3 4 5)
+  (assert-equal (#%(identity [%1 (, %2 [%3] "Hy" [%*])]) 1 2 3 4 5)
                 [1 (, 2 [3] "Hy" [(, 4 5)])])
   ;; test arg as function
-  (assert-equal ((xi x1 2 4) +) 6)
+  (assert-equal (#%(%1 2 4) +) 6)
-  (assert-equal ((xi x1 2 4) -) -2)
+  (assert-equal (#%(%1 2 4) -) -2)
-  (assert-equal ((xi x1 2 4) /) 0.5))
+  (assert-equal (#%(%1 2 4) /) 0.5)
+  ;; test &rest &kwargs
+  (assert-equal (#%(, %* %**) 1 2 :a 'b)
+                (, (, 1 2)
+                   (dict :a 'b)))
+  ;; test other expression types
+  (assert-equal (#% %* 1 2 3)
+                (, 1 2 3))
+  (assert-equal (#% %** :foo 2)
+                (dict :foo 2))
+  (assert-equal (#%[%3 %2 %1] 1 2 3)
+                [3 2 1])
+  (assert-equal (#%{%1 %2} 10 100)
+                {10 100})
+  (assert-equal (#% #{%3 %2 %1} 1 3 2)
+                #{3 1 2})  ; sets are not ordered.
+  (assert-equal (#% "%1")
+                "%1"))
+