make 'memo' available

nifty4/__init__.py

@@ -20,6 +20,8 @@ from .plotting.plot import plot
 from . import library
 from . import extra
 
+from .utilities import memo
+
 __all__ = ["__version__", "dobj", "DomainTuple"] + \
           domains.__all__ + operators.__all__ + minimization.__all__ + \
           ["DomainTuple", "Field", "sqrt", "exp", "log"]