NEWS and docs for hy-repr

NEWS.rst

@@ -7,6 +7,14 @@ Bug Fixes
 ------------------------------
 * Fix `(return)` so it works correctly to exit a Python 2 generator
 
+Other Breaking Changes
+-----------------------------
+* `hy-repr` uses registered functions instead of methods
+
+Misc. Improvements
+----------------------------
+* `hy-repr` supports more standard types
+
 0.14.0
 ==============================
 

docs/contrib/hy_repr.rst

@@ -4,10 +4,10 @@ Hy representations
 
 .. versionadded:: 0.13.0
 
-``hy.contrib.hy-repr`` is a module containing a single function.
+``hy.contrib.hy-repr`` is a module containing two functions.
-To import it, say::
+To import them, say::
 
-  (import [hy.contrib.hy-repr [hy-repr]])
+  (import [hy.contrib.hy-repr [hy-repr hy-repr-register]])
 
 To make the Hy REPL use it for output, invoke Hy like so::
 
@@ -30,19 +30,47 @@ It returns a string representing the input object in Hy syntax.
    => (repr [1 2 3])
    '[1, 2, 3]'
 
-If the input object has a method ``__hy-repr__``, it will be called
-instead of doing anything else.
-
-.. code-block:: hy
-
-  => (defclass C [list] [__hy-repr__ (fn [self] "cuddles")])
-  => (hy-repr (C))
-  'cuddles'
-
-When ``hy-repr`` doesn't know how to handle its input, it falls back
-on ``repr``.
-
 Like ``repr`` in Python, ``hy-repr`` can round-trip many kinds of
 values. Round-tripping implies that given an object ``x``,
 ``(eval (read-str (hy-repr x)))`` returns ``x``, or at least a value
 that's equal to ``x``.
+
+.. _hy-repr-register-fn:
+
+hy-repr-register
+----------------
+
+Usage: ``(hy-repr-register the-type fun)``
+
+``hy-repr-register`` lets you set the function that ``hy-repr`` calls to
+represent a type.
+
+.. code-block:: hy
+
+    => (defclass C)
+    => (hy-repr-register C (fn [x] "cuddles"))
+    => (hy-repr [1 (C) 2])
+    '[1 cuddles 2]'
+
+If the type of an object passed to ``hy-repr`` doesn't have a registered
+function, ``hy-repr`` will search the type's method resolution order
+(its ``__mro__`` attribute) for the first type that does. If ``hy-repr``
+doesn't find a candidate, it falls back on ``repr``.
+
+Registered functions often call ``hy-repr`` themselves. ``hy-repr`` will
+automatically detect self-references, even deeply nested ones, and
+output ``"..."`` for them instead of calling the usual registered
+function. To use a placeholder other than ``"..."``, pass a string of
+your choice to the keyword argument ``:placeholder`` of
+``hy-repr-register``.
+
+.. code-block:: hy
+
+   (defclass Container [object]
+     [__init__ (fn [self value]
+       (setv self.value value))])
+   (hy-repr-register Container :placeholder "HY THERE" (fn [x]
+     (+ "(Container " (hy-repr x.value) ")")))
+   (setv container (Container 5))
+   (setv container.value container)
+   (print (hy-repr container))  ; Prints "(Container HY THERE)"