Foreign code can set or create Prolog flags using PL_set_prolog_flag().
See set_prolog_flag/2
and create_prolog_flag/3.
To retrieve the value of a flag you can use PL_current_prolog_flag().
- bool PL_set_prolog_flag(const
char *name, int type, ...)
- Set/create a Prolog flag from C. name is the name of the
affected flag. type is one of the values below, which also
dictates the type of the final argument. The function returns
TRUE on success and FALSE on failure. This
function can be called before PL_initialise(),
making the flag available to the Prolog startup code.
PL_BOOL- Create a boolean (
true or false) flag. The
argument must be an int.
PL_ATOM- Create a flag with an atom as value. The argument must be of type
const char *.
PL_INTEGER- Create a flag with an integer as value. The argument must be of type
intptr_t *.
- int PL_current_prolog_flag(atom_t
name, int type, void *value)
- Retrieve the value of a Prolog flag from C. name is the name
of the flag as an
atom_t (see current_prolog_flag/2).
type specifies the kind of value to be retrieved, it is one
of the values below. value is a pointer to a location where
to store the value. The user is responsible for making sure this memory
location is of the appropriate size/type (see the returned types below
to determine the size/type). The function returns TRUE on
success and FALSE on failure.
PL_ATOM- Retrieve a flag whose value is an
atom. The returned value
is an atom handle of type atom_t.
PL_INTEGER- Retrieve a flag whose value is an
integer. The returned
value is an integer of type int64_t.
PL_FLOAT- Retrieve a flag whose value is a
float. The returned value
is a floating point number of type double.
PL_TERM- Retrieve a flag whose value is a
term. The returned value
is a term handle of type term_t.
