Templates
Description
functor(Term, Name, Arity) succeeds if the principal functor of Term is Name and its arity is Arity. This predicate can be used in two ways:
Errors
| Term and Name are both variables | instantiation_error | |
| Term and Arity are both variables | instantiation_error | |
| Term is a variable and Name is neither a variable nor an atomic term | type_error(atomic, Name) | |
| Term is a variable and Arity is neither a variable nor an integer | type_error(integer, Arity) | |
| Term is a variable, Name is a constant but not an atom and Arity is an integer > 0 | type_error(atom, Name) | |
| Term is a variable and Arity is an integer > max_arity flag (section 7.22.1) | representation_error(max_arity) | |
| Term is a variable and Arity is an integer < 0 | domain_error(not_less_than_zero, Arity) | |
Portability
ISO predicate.
Templates
Description
arg(N, Term, Arg) succeeds if the Nth argument of Term is Arg.
Errors
| N is a variable | instantiation_error | |
| Term is a variable | instantiation_error | |
| N is neither a variable nor an integer | type_error(integer, N) | |
| Term is neither a variable nor a compound term | type_error(compound, Term) | |
| N is an integer < 0 | domain_error(not_less_than_zero, N) | |
Portability
ISO predicate.
Templates
Description
Term =.. List succeeds if List is a list whose head is the atom corresponding to the principal functor of Term and whose tail is a list of the arguments of Term.
=.. is a predefined infix operator (section 7.14.10).
Errors
| Term is a variable and List is a partial list | instantiation_error | |
| List is neither a partial list nor a list | type_error(list, List) | |
| Term is a variable and List is a list whose head is a variable | instantiation_error | |
| List is a list whose head H is neither an atom nor a variable and whose tail is not the empty list | type_error(atom, H) | |
| List is a list whose head H is a compound term and whose tail is the empty list | type_error(atomic, H) | |
| Term is a variable and List is the empty list | domain_error(non_empty_list, []) | |
| Term is a variable and the tail of List has a length > max_arity flag (section 7.22.1) | representation_error(max_arity) | |
Portability
ISO predicate.
Templates
Description
copy_term(Term1, Term2) succeeds if Term2 unifies with a term T which is a renamed copy of Term1.
Errors
None.
Portability
ISO predicate.
Templates
Description
setarg(N, Term, NewValue, Undo) replaces destructively the Nth argument of Term with NewValue. This assignment is undone on backtracking if Undo = true. This should only used if there is no further use of the old value of the replaced argument. If Undo = false then NewValue must be either an atom or an integer.
setarg(N, Term, NewValue) is equivalent to setarg(N, Term, NewValue, true).
Errors
| N is a variable | instantiation_error | |
| N is neither a variable nor an integer | type_error(integer, N) | |
| N is an integer < 0 | domain_error(not_less_than_zero, N) | |
| Term is a variable | instantiation_error | |
| Term is neither a variable nor a compound term | type_error(compound, Term) | |
| NewValue is neither an atom nor an integer and Undo = false | type_error(atomic, NewValue) | |
| Undo is a variable | instantiation_error | |
| Undo is neither a variable nor a boolean | type_error(boolean, Undo) | |
Portability
GNU Prolog predicate.