curry.py

__all__ = ['curry']

# Modified from http://mtomassoli.wordpress.com/2012/03/18/currying-in-python/
# Not perfect, but almost there

# Note: func_name must be ascii string
def generate_curry_func_name(func, *args, **kwargs):
    argument = map(repr, args)
    argument += [u'%s=%s' % (k,repr(kwargs[k])) for k in func.func_code.co_varnames if k in kwargs]
    argument = u', '.join(argument)
    return func.func_name + ('(%s)' % argument.encode('raw_unicode_escape') if argument else '')

def curry(func, unique_kwargs=True, require_force_evaluate=False):
    """ Generates a 'curried' version of a function.
    
        Example:
         >>> @curry
         >>> def f(a,b,c,d=1,e=2,f=3):
         ...     print 'Hello', a, b, c, d, e, f
         ...
         >>> f(1,f=1)(c=3, d=3)(2)
         Hello 1 2 3 3 2 1
    """
    num_default_args = len(func.func_defaults)
    required_args = set(func.func_code.co_varnames[:-num_default_args])
    
    def g(*args, **kwargs):
        def f(*_args, **_kwargs):
            if _args or _kwargs:
                new_args = args + _args
                new_kwargs = dict.copy(kwargs)
                
                if unique_kwargs and not set(_kwargs.keys()).isdisjoint(new_kwargs):
                    raise ValueError('Duplicate keyword argument while currying')
                
                new_kwargs.update(_kwargs)
                
                # check whether it's time to evaluate
                if not require_force_evaluate and \
                 len(required_args.intersection(new_kwargs.keys())) + \
                 len(new_args) >= len(required_args):
                    return func(*new_args, **new_kwargs)
                else:
                    return g(*new_args, **new_kwargs)
            else:
                # force evaluation
                return func(*args, **kwargs)
        
        f.func_name = generate_curry_func_name(func, *args, **kwargs)
        return f
    
    return g()