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Unification (version 2) |
See also section 2.13.1.
*blob==nullptr
.
A family of unification methods are defined for the various Prolog
types and C++ types. Wherever string
is shown, you can use:
char*
whar_t*
std::string
std::wstring
Here is an example:
PREDICATE(hostname, 1) { char buf[256]; if ( gethostname(buf, sizeof buf) == 0 ) return A1.unify_atom(buf); return false; }
An alternative way of writing this would use the PlCheckFail() to raise an exception if the unification fails.
PREDICATE(hostname2, 1) { char buf[256]; PlCheckFail(gethostname(buf, sizeof buf) == 0); PlCheckFail(A1.unify_atom(buf)); return true; }
Of course, in a real program, the failure of
gethostname(buf)sizeof buf should create an error term than
contains information from errno
.