de

ummels

package ummels

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  1. package prioritymap

    Provides an implementation of immutable priority maps, i.e.

    Provides an implementation of immutable priority maps, i.e. immutable maps that return their entries sorted by value.

    Overview

    Priority maps are similar to sorted maps, but while for sorted maps iterator returns an iterator that produces entries sorted by their keys, calling iterator on a priority map returns an iterator that produces entries sorted by their values. Priority maps also offer several range methods, which return a submap with values inside a given range.

    Since calling head on a priority map returns a key-value pair with minimal value, priority maps can also be thought of as a more versatile variant of priority queues.

    Usage

    The easiest way to instantiate a new priority map is to use the apply method in the de.ummels.prioritymap.PriorityMap companion object.

    scala> val m = PriorityMap('a' -> 1, 'b' -> 2, 'c' -> 0)
m: de.ummels.prioritymap.PriorityMap[Char,Int] = PriorityMap(c -> 0, a -> 1, b -> 2)

    Since priority maps are immutable, updating a key/value pair returns a new map and does not modify the old map.

    scala> m + ('b' -> -1)
res1: de.ummels.prioritymap.PriorityMap[Char,Int] = PriorityMap(b -> -1, c -> 0, a -> 1)

scala> m
res2: de.ummels.prioritymap.PriorityMap[Char,Int] = PriorityMap(c -> 0, a -> 1, b -> 2)

    In addition to the methods available for maps, priority maps offer methods for obtaining a submap whose values lie inside a given range.

    scala> m.from(1)
res3: de.ummels.prioritymap.PriorityMap[Char,Int] = PriorityMap(a -> 1, b -> 2)

scala> m.until(2)
res4: de.ummels.prioritymap.PriorityMap[Char,Int] = PriorityMap(c -> 0, a -> 1)

scala> m.range(1, 2)
res5: de.ummels.prioritymap.PriorityMap[Char,Int] = PriorityMap(a -> 1)

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