Examining the program

current_atom1-Atom Successively unifies Atom with all atoms known to the system. Note that current_atom1 always succeeds if Atom is instantiated to an atom. current_functor2?Name, ?Arity Successively unifies Name with the name and Arity with the arity of functors known to the system. current_flag1-FlagKey Successively unifies FlagKey with all keys used for flags (see flag3). current_key1-Key Successively unifies Key with all keys used for records (see recorda3, etc.). current_predicate2?Name, ?Head Successively unifies Name with the name of predicates currently defined and Head with the most general term built from Name and the arity of the predicate. This predicate succeeds for all predicates defined in the specified module, imported to it, or in one of the modules from which the predicate will be imported if it is called. predicate_property2?Head, ?Property Succeeds if Head refers to a predicate that has property Property. Can be used to test whether a predicate has a certain property, obtain all properties known for Head, find all predicates having property or even obtaining all information available about the current program. Property is one of:

interpreted Is true if the predicate is defined in Prolog. We return true on this because, although the code is actually compiled, it is completely transparent, just like interpreted code. built_in Is true if the predicate is locked as a built-in predicate. This implies it cannot be redefined in its definition module and it can normally not be seen in the tracer. foreign Is true if the predicate is defined in the C language. dynamic Is true if the predicate is declared dynamic using the dynamic1 declaration. multifile Is true if the predicate is declared multifile using the multifile1 declaration. undefined Is true if a procedure definition block for the predicate exists, but there are no clauses in it and it is not declared dynamic. This is true if the predicate occurs in the body of a loaded predicate, an attempt to call it has been made via one of the meta-call predicates or the predicate had a definition in the past. See the library package check for example usage. transparent Is true if the predicate is declared transparent using the module_transparent1 declaration. exported Is true if the predicate is in the public list of the context module. imported_fromModule Is true if the predicate is imported into the context module from module Module. indexedHead Predicate is indexed (see index1) according to Head. Head is a term whose name and arity are identical to the predicate. The arguments are unified with `1' for indexed arguments, `0' otherwise. fileFileName Unify FileName with the name of the sourcefile in which the predicate is defined. See also source_file2. line_countLineNumber Unify LineNumber with the line number of the first clause of the predicate. Fails if the predicate is not associated with a file. See also source_file2. number_of_clausesClauseCount Unify ClauseCount to the number of clauses associated with the predicate. Fails for foreign predicates.

dwim_predicate2+Term, -Dwim `Do What I Mean' (`dwim') support predicate. Term is a term, which name and arity are used as a predicate specification. Dwim is instantiated with the most general term built from Name and the arity of a defined predicate that matches the predicate specified by Term in the `Do What I Mean' sense. See dwim_match2 for `Do What I Mean' string matching. Internal system predicates are not generated, unless style_check(+dollar) is active. Backtracking provides all alternative matches. clause2?Head, ?Body Succeeds when Head can be unified with a clause head and Body with the corresponding clause body. Gives alternative clauses on backtracking. For facts Body is unified with the atom true. Normally clause2 is used to find clause definitions for a predicate, but it can also be used to find clause heads for some body template. clause3?Head, ?Body, ?Reference Equivalent to clause2, but unifies Reference with a unique reference to the clause (see also assert2, erase1). If Reference is instantiated to a reference the clause's head and body will be unified with Head and Body. nth_clause3?Pred, ?Index, ?Reference Provides access to the clauses of a predicate using their index number. Counting starts at 1. If Reference is specified it unifies Pred with the most general term with the same name/arity as the predicate and Index with the index-number of the clause. Otherwise the name and arity of Pred are used to determine the predicate. If Index is provided Reference will be unified with the clause reference. If Index is unbound, backtracking will yield both the indices and the references of all clauses of the predicate. The following example finds the 2nd clause of member2:

clause_property2+ClauseRef, -Property Queries properties of a clause. ClauseRef is a reference to a clause as produced by clause3, nth_clause3 or prolog_frame_attribute3. Property is one of the following:

fileFileName Unify FileName with the name of the sourcefile in which the clause is defined. Fails if the clause is not associated to a file. line_countLineNumber Unify LineNumber with the line number of the clause. Fails if the clause is not associated to a file. fact True if the clause has no body. erased True if the clause has been erased, but not yet reclaimed because it is referenced.