make_overloadable : string -> hol_type -> unit
Makes a symbol overloadable within the specified type skeleton.
HOL Light allows the same identifier to denote several different underlying
constants, with the choice being determined by types and/or an order of
priority (see prioritize_overload). However, any identifier ident to be
overloaded must first be declared overloadable using
make_overloadable "ident" `:ty`. The ``type skeleton'' argument `:ty` is
the most general type that the various instances may have.
The type skeleton can simply be a type variable, in which case any type is
acceptable, but it is good practice to constrain it where possible to allow
more information to be inferred during typechecking. For example, the symbol
`+' has the type skeleton `:A->A->A` (as you can find out by examining the
list the_overload_skeletons) indicating that it is always overloaded to a
binary operator that returns and element of the same type as its two arguments.
- FAILURE CONDITIONS
Fails if the symbol has previously been made overloadable but with a different
# make_overloadable "<=" `:A->A->bool`;;
val it : unit = ()
- SEE ALSO
overload_interface, override_interface, prioritize_overload, reduce_interface,
remove_interface, the_implicit_types, the_interface, the_overload_skeletons.