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|Pack canny_tudor -- prolog/swi/options.pl|
Defaults are unbound if not present. The implementation selects an
option's Default from the given list of Defaults using
select_option/4. Option terms must have one variable. This is
because select_option/4's fourth argument is a single argument. It
never unifies with multiple variables even though it succeeds, e.g.
select_option(a(A, B), , Rest, 1) unifies A with 1, leaving B
There is a naming issue. What to call the incoming list of Option arguments and the Options argument with which the Option terms unify? One possibility: name the Options argument RestOptions0 since they represent the initial set of RestOptions from which Options select. This clashes with select_option/4's naming convention since Options is the argument name for RestOptions0's role in the option-selection process. Nevertheless, this version follows this renamed argument convention.