The list below summarises the classes defined in the C++ interface.
- PlTerm
- Generic Prolog term that wraps
term_t (for more details on term_t,
see
Interface
Data Types).
This is a “base class” whose constructor is protected;
subclasses specify the actual contents. Additional methods allow
checking the Prolog type, unification, comparison, conversion to native
C++-data types, etc. See section
1.11.1.
For more details about PlTerm, see section
1.6.6
- PlCompound
- Subclass of
PlTerm with constructors for building compound
terms. If there is a single string argument, then PL_chars_to_term()
or PL_wchars_to_term() is used to parse the string and create the
term. If the constructor has two arguments, the first is name of a
functor and the second is a PlTermv with the arguments.
- PlTermv
- Vector of Prolog terms. See PL_new_term_refs(). The
[]PlTermv
is used to build complex terms and provide argument-lists to Prolog
goals.
- PlAtom
- Wraps
atom_t in their internal Prolog representation for
fast comparison. (For more details on
atom_t, see
Interface
Data Types). For more details of PlAtom, see section
1.11.12.4.
- PlFunctor
- A wrapper for
functor_t, which maps to the internal
representation of a name/arity pair.
- PlPredicate
- A wrapper for
predicate_t, which maps to the internal
representation of a Prolog predicate.
- PlModule
- A wrapper for
module_t, which maps to the internal
representation of a Prolog module.
- PlQuery
- Represents opening and enumerating the solutions to a Prolog query.
- PlException
- If a call to Prolog results in an error, the C++ interface converts the
error into a
PlException object and throws it. If the
enclosing code doesn't intercept the exception, the PlException
object is turned back into a Prolog error when control returns to Prolog
from the PREDICATE() macros.
This is a subclass of PlExceptionBase, which is a subclass
of std::exception.
- PlFrame
- This utility-class can be used to discard unused term-references as well
as to do data-backtracking.
- PlEngine
- This class is used in embedded applications (applications where
the main control is held in C++). It provides creation and destruction
of the Prolog environment.
- PlRegister
- Encapsulates PL_register_foreign() to allow using C++ global
constructors for registering foreign predicates.
- PlFail
- Can be thrown to short-circuit processing and return failure to Prolog.
Performance-critical code should use
return false instead
if failure is expected. An error can be signaled by calling
Plx_raise_exception() or one of the PL_*_error() functions
and then throwing PlFail; but it's better style to create
the error throwing one of the subclasses of PlException
e.g.,
throw PlTypeError("int", t). Subclass of PlExceptionFailBase.
- PlExceptionFail
- In some situations, a Prolog error cannot be turned into a
PlException object, so a PlExceptionFail
object is thrown. This is turned into failure by the PREDICATE()
macro, resulting in normal Prolog error handling. Subclass of PlExceptionFailBase.
- PlExceptionBase
- A “do nothing” subclass of
std::exception, to
allow catching
PlException, PlExceptionFail or PlFail
in a single “catch” clause.
- PlExceptionFailBase
- A “do nothing” subclass of
PlExceptionBase, to
allow catching
PlExceptionFail or PlFail in a single “catch” clause,
excluding PlException.
