Term References

Functions:

1. X_API term_t PL_new_term_ref(void): : create a clean term reference

1. X_API term_t PL_copy_term_ref(term_t from): : duplicate a term reference

1. X_API term_t PL_new_term_refs(int n): : create several new term references

n is the number of references

1. X_API void PL_reset_term_refs(term_t after): : dispose of all term references created since after