Here is a list of all files with brief descriptions:

all_different.hpp
all_equal.hpp
auxiliary_data.hpp
constraint.hpp
fix_value.hpp
linear_equation.hpp
linear_equation_eq.hpp
linear_equation_g.hpp
linear_equation_geq.hpp
linear_equation_l.hpp
linear_equation_leq.hpp
linear_equation_neq.hpp
model_builder.hpp
objective.hpp
options.hpp
print.hpp
solver.hpp
variable.hpp