Make Curry a class and curry a function. Working on pytoolz#147. …

…Not finished.

This includes a significant change to curried objects: they never return
`functools.partial` objects.  Instead, `Curry` *uses* `partial`.  This
is because `partial` behaves differently.  Let me illustrate:

`curry(lambda x, y=0: x+y)(y=2)` is valid.
`partial(lambda x, y=0: x+y)(y=2)` returns a TypeError.

More documentation and tests are needed.  PRs (and comments) are welcome.

toolz/functoolz/core.py

@@ -105,7 +105,45 @@ def _num_required_args(func):
         return None
 
 
-class curry(object):
+class Curry(object):
+    def __init__(self, func, *args, **kwargs):
+        if not callable(func):
+            raise TypeError("Input must be callable")
+
+        if kwargs:
+            self.partial = partial(func, *args, **kwargs)
+        else:
+            self.partial = partial(func, *args)
+        self.func = self.partial.func
+        self.args = self.partial.args
+        self.keywords = self.partial.keywords
+        self.__doc__ = self.func.__doc__
+        try:
+            self.func_name = self.func.func_name
+        except AttributeError:
+            pass
+
+    def __str__(self):
+        return str(self.func)
+
+    def __repr__(self):
+        return repr(self.func)
+
+    def __call__(self, *args, **kwargs):
+        try:
+            return self.partial(*args, **kwargs)
+        except TypeError:
+            required_args = _num_required_args(self.func)
+
+            # If there was a genuine TypeError
+            if (required_args is not None and
+                    len(args) + len(self.args) >= required_args):
+                raise
+
+            return curry(self.partial, *args, **kwargs)
+
+
+def curry(func, *args, **kwargs):
     """ Curry a callable function
 
     Enables partial application of arguments through calling a function with an
@@ -133,54 +171,21 @@ class curry(object):
         toolz.curried - namespace of curried functions
                         http://toolz.readthedocs.org/en/latest/curry.html
     """
-    def __init__(self, func, *args, **kwargs):
-        if not callable(func):
-            raise TypeError("Input must be callable")
-
-        self.func = func
-        self.args = args
-        self.keywords = kwargs if kwargs else None
-        self.__doc__ = self.func.__doc__
-        try:
-            self.func_name = self.func.func_name
-        except AttributeError:
-            pass
-
-    def __str__(self):
-        return str(self.func)
-
-    def __repr__(self):
-        return repr(self.func)
-
-    def __call__(self, *args, **_kwargs):
-        args = self.args + args
-        if _kwargs:
-            kwargs = {}
-            if self.keywords:
-                kwargs.update(self.keywords)
-            kwargs.update(_kwargs)
-        elif self.keywords:
-            kwargs = self.keywords
-        else:
-            kwargs = {}
-
-        try:
-            return self.func(*args, **kwargs)
-        except TypeError:
-            required_args = _num_required_args(self.func)
-
-            # If there was a genuine TypeError
-            if required_args is not None and len(args) >= required_args:
-                raise
-
-            # If we only need one more argument
-            if (required_args is not None and required_args - len(args) == 1):
-                if kwargs:
-                    return partial(self.func, *args, **kwargs)
-                else:
-                    return partial(self.func, *args)
-
-            return curry(self.func, *args, **kwargs)
+    if not callable(func):
+        raise TypeError("Input must be callable")
+
+    # Curry- or functools.partial-like object?  Unpack and merge arguments
+    if (hasattr(func, 'func') and hasattr(func, 'args')
+            and hasattr(func, 'keywords')):
+        _kwargs = {}
+        if func.keywords:
+            _kwargs.update(func.keywords)
+        _kwargs.update(kwargs)
+        kwargs = _kwargs
+        args = func.args + args
+        func = func.func
+
+    return Curry(func, *args, **kwargs)
 
 
 @curry