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12.12 data.priority-map - Priority map

Module: data.priority-map

Priority map is a dictionary that can map keys to values, while the entires are sorted by their values. (If the entires are sorted by keys, it’s a treemap–see Treemaps).

It is useful when you wanted a sorted sequence, with quick access by keys that are associated to each value.

Note: If what you need is just a priority queue, you can use data.heap (see Heap).

Class: <priority-map>

{data.priority-map} Priority map class. It has no public slots. Instances of priority maps must be created by make-priority-map procedure instead of make method on the class.

Inherits <ordered-dictionary>, and implements dictionary protocol. Operations concerning associations of keys and values are done through dictionary generic functions (see Generic functions for dictionaries).

When iterated, it iterates increasing order of values.

Function: make-priority-map :key key-comparator value-comparator

{data.priority-map} Creates and returns an empty priority map. It can take key-comparator, which must have a hash procedure and is used to hash keys, and value-comparator, which must have ordering predicate and is used to order values. When omitted, default-comparator is assumed.

Function: priority-map-min pmap
Function: priority-map-max pmap

{data.priority-map} Return a pair of a key and a value, where the value is smallest or largest in the priority map pmap, respectively.

If pmap is empty, #f is returned.

If pmap has more than one value that are equal to each other (w.r.t. value-comparator given to the constructor), either one of them is picked.

Function: priority-map-pop-min! pmap
Function: priority-map-pop-max! pmap

{data.priority-map} Remove one entry with the smallest or largest value, respectively, and returns a pair of the key and the value of removed entry.

If pmap is empty, #f is returned.

If pmap has more than one value that are equal to each other (w.r.t. value-comparator given to the constructor), either one of them is picked.


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