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Analysing compound terms (version 2) |
Compound terms can be viewed as an array of terms with a name and
arity (length). This view is expressed by overloading the
operator.
[]
A type_error
is raised if the argument is not compound
and a
domain_error
if the index is out of range.
In addition, the following functions are defined:
PlTerm
is a compound term and arg is
between 1 and the arity of the term, return a new PlTerm
representing the arg-th argument of the term. If PlTerm
is
not compound, a
type_error
is raised. Id arg is out of range, a
domain_error
is raised. Please note the counting from 1
which is consistent to Prolog's arg/3
predicate, but inconsistent to C's normal view on an array. See also
class PlCompound
. The following example tests x
to represent a term with first-argument an atom or string equal to gnat
.
..., if ( x[1] == "gnat" ) ...
const char *
holding the name of the functor of
the compound term. Raises a type_error
if the argument is
not compound.type_error
if the argument is not compound.