Meta-properties

Author(s): Francisco Bueno.

This library allows the use of some meta-constructs which provide for specifying properties of terms which are unknown at the time of the specification, or expressed with a shorthand for the property definition, i.e., without really defining it.

An example of such use is an assertion which specifies that any property holding upon call will also hold upon exit:

         :- pred p(X) : Prop(X) => Prop(X).
        

Another example is using shorthands for properties when documenting:

         :- pred p(X) : regtype(X,(^(list;list);list)).
        

(See below for an explanation of such a regular type.)

Usage and interface

Documentation on exports

PROPERTY
call(P,A)

A has property P (provided that P is a property). Equivalent to P(A).

Usage: call(P,A)

  • Description: A has property P.
  • If the following properties hold at call time:
    (callable/1)P is a term which represents a goal, i.e., an atom or a structure.

PROPERTY

Usage: A prop P

  • Description: A has property P.
  • If the following properties hold at call time:
    ((prop)/2)P has property ^ (callable;prop_abs).

PROPERTY

Usage: A regtype T

  • Description: A is of type T.
  • If the following properties hold at call time:
    ((prop)/2)T has property ^ ((regtype);prop_abs).

Documentation on multifiles

PREDICATE
(User defined.) A hook predicate you have to define as callme(P,X):- P(X), !. in the program that uses this library. This is done automatically if the package is used instead of the library module (but then you should not define callme/2 in your program).
The predicate is multifile.

Usage: callme(A,B)

  • The following properties should hold at call time:
    (callable/1)A is a term which represents a goal, i.e., an atom or a structure.

Documentation on internals

PROPERTY
prop_abs(Prop)

Prop is a property abstraction, i.e., a parametric property, or a term formed of property abstractions, where the functors used in the term are escaped by ^.

One particular case of property abstractions are parametric regular type abstractions, i.e., a parametric type functor or a ^-escaped term formed of regular type abstractions.

Such abstractions are a short-hand for a corresponding regular type (correspondingly, property). For example, the following abstraction:

         ^(list;list);list
        
denotes terms of the form (X;Y) where list(X) and list(Y) hold and also terms T such that list(T) holds. It is equivalent to the regular type:
         abstract_type((X;Y)):- list(X), list(Y).
         abstract_type(T):- list(T).
        

Usage: prop_abs(Prop)