2.2 Sample code (version 2)

The file test_cpp.cpp contains examples of Prolog predicates written in C++. This file is used for testing (called from test_cpp.pl). Notable examples:

• add_num/3 - same as A3 is A1+A2, converting the sum to an integer if possible.
• name_arity/3 - C++ implementation of functor/3.
• average/3 - computes the average of all the solutions to Goal
• can_unify/2 - tests whether the two arguments can unify with each other, without instantiating anything (similar to unifiable/3).
• eq1/1, eq2/2, eq3/2 - three different ways of implementing =/2.
• write_list/1 - outputs the elements of a list, each on a new line.
• cappend/3 - appends two lists (requires that the two lists are instantiated).
• square_roots/2 - same as bagof(Sqrt, X^(between(0,4,X), Sqrt is sqrt(X)), A2).
• range_cpp/3 - on backtracking, generates all integers starting at A1 and less than A2 (that is, one less than between/3).
• int_info/2 - on backtracking generates all the integral types with their minimum and maximum values.

The file likes.cpp contains a simple program that calls the Prolog predicate likes/2 and happy/1 (these predicates are defined in likes.pl. The usage and how to compile the code are in comments in likes.cpp