b_external(++PredSpec)

PredSpec

Of the form Atom/Integer (predicate name/arity).

This built-in predicate is obsolete!

Description

This declaration is needed to compile calls to an external predicate before it is actually defined with b_external/2.

Modes and Determinism

• b_external(++) is det

Modules

Exceptions

(4) instantiation fault

PredSpec is not instantiated.

(5) type error

PredSpec is not of the form Atom/Integer.

(62) inconsistent procedure redefinition

A call to PredSpec has already been compiled as a deterministic external call.

Examples

Success:

   % compiling a call to an external before its definition (see description
   % of b_external/2 for detail on creating external predicates).
      [eclipse]: [user].
       :- import sines/2 from trig_lib.
       :- b_external(sines/2). % declare its call_type
       p(Values) :- sines(Res, Values), writeln(Res), fail.
       p(_).
       user      compiled 216 bytes in 0.03 seconds

   % definition of sines/2 will not raise an inconsistent type definition
   % thanks to the proper declaration above.
      [eclipse]: sh("cat trig_lib.pl").
      :- module(trig_lib).
      :- load('sin.o', "-lm"). % see example in b_external/2
      :- b_external(sines/2, p_sines).
      :- export sines/2.

      yes
      [eclipse]: [trig_lib].
       trig_lib.pl      compiled 0 bytes in 0.18 seconds
      yes.
      [eclipse]: p([0.0,45.0,90.0,270.0]).
      0.0
      0.707107
      1.0
      -1.0
      yes.

Error:
      b_external(PredSpec).         (Error 4).
      b_external("p/0").            (Error 5).

      [eclipse]: [user].
       :- external(a/0).
       p :- a.
       user   compiled 32 bytes in 0.00 seconds
      yes.
      [eclipse]: b_external(a/0).     (Error 62).

See Also