A.46 library(rbtrees): Red black trees
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Availability::- use_module(library(rbtrees)).(can be autoloaded)
Source[nondet]rb_in(?Key, ?Value, +Tree)
True when Key-Value is a key-value pair in red-black tree Tree. Same as below, but does not materialize the pairs. 
rb_visit(Tree, Pairs), member(Key-Value, Pairs)

Leaves a choicepoint even if Key is instantiated; to avoid a choicepoint, use rb_lookup/3.

ClioPatria (version V3.1.1-51-ga0b30a5)