1.12.1 The C++ versus the C interface

Not all functionality of the C-interface is provided, but as PlTerm and term_t are essentially the same thing with automatic type-conversion between the two, this interface can be freely mixed with the functions defined for plain C.

Using this interface rather than the plain C-interface requires a little more resources. More term-references are wasted (but reclaimed on return to Prolog or using PlFrame). Use of some intermediate types (functor_t etc.) is not supported in the current interface, causing more hash-table lookups. This could be fixed, at the price of slighly complicating the interface.