is_perc verifies a percentage;
is_prob verifies a probability;
is_valid_prob_set verifies the validity of probability inputs;
num contains basic numeric variables;
init_num initializes basic numeric variables;
prob contains current probability information;
comp_prob computes current probability information;
freq contains current frequency information;
comp_freq computes current frequency information;
comp_complement computes a probability's complement;
comp_comp_pair computes pairs of complements.
Other utility functions: as_pc,
plot.box
Other display functions: as_pc