SWI-Prolog -- API-function PL_term

Availability:C-language interface function

int PL_term_type(term_t)

Obtain the type of a term, which should be a term returned by one of the other interface predicates or passed as an argument. The function returns the type of the Prolog term. The type identifiers are listed below. Note that the extraction functions PL_get_*() also validate the type and thus the two sections below are equivalent.

        if ( PL_is_atom(t) )
        { char *s;

          PL_get_atom_chars(t, &s);
          ...;
        }

or

        char *s;
        if ( PL_get_atom_chars(t, &s) )
        { ...;
        }

Version 7 added PL_NIL, PL_BLOB, PL_LIST_PAIR and PL_DICT. Older versions classify PL_NIL and PL_BLOB as PL_ATOM, PL_LIST_PAIR as PL_TERM and do not have dicts.

`PL_VARIABLE`	A variable or attributed variable
`PL_ATOM`	A Prolog atom
`PL_NIL`	The constant `[]`
`PL_BLOB`	A blob (see section 12.4.9.2)
`PL_STRING`	A string (see section 5.2)
`PL_INTEGER`	A integer
`PL_RATIONAL`	A rational number
`PL_FLOAT`	A floating point number
`PL_TERM`	A compound term
`PL_LIST_PAIR`	A list cell (`[H\|T]`)
`PL_DICT`	A dict (see section 5.4))