Curry: An Integrated Functional Logic Language

import stack
imports all entities exported by the module stack, whereas the declaration
import family(father, grandfather)
imports only the entities father and grandfather from the module family, provided that they
are exported by family. Similarly to export declarations, a datatype name t in an import list
imports only the datatype without its constructors whereas the form t(..) imports the datatype
together with all its constructors (provided that they are also exported).
The names of all imported entities are accessible in the current module, i.e., they are equivalent
to top-level declarations, provided that their names are not in conflict with other names. For
instance, if a function f is imported from module m but the current module contains a top-level
declaration for f (which is thus directly accessible in the current module), the imported function is
not accessible (without qualification). Similarly, if two identical names are imported from different
modules and denote different entities, none of these entities is accessible (without qualification). It
is possible to refer to such imported but not directly accessible names by prefixing them with the
module identifier (qualification). For instance, consider the module m1 defined by
module m1 where
f :: Int -> Int
...
and the module m2 defined by
module m2 where
f :: Int -> Int
...
together with the main module
module main where
import m1
import m2
...
Then the names of the imported functions f are not directly accessible in the main module but one
can refer to the corresponding imported entities by the qualified identifiers m1.f or m2.f.
Another method to resolve name conflicts between imported entities is the qualification of an
imported module. If we change the main module to
module main where
import qualified m1
import m2
...
then the name f refers to the entity m2.f since all entities imported from m1 are only accessible by
qualification like m1.f.
A further method to avoid name conflicts is the hiding of imported entities. Consider the
following definition:
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