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https://github.com/Nycto/RBTreeNim

Nim Red/Black Trees
https://github.com/Nycto/RBTreeNim

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Nim Red/Black Trees

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README 

        
RBTreeNim

=========



[![Build](https://github.com/Nycto/RBTreeNim/actions/workflows/build.yml/badge.svg)](https://github.com/Nycto/RBTreeNim/actions/workflows/build.yml)

[![License](https://img.shields.io/badge/License-MIT-blue.svg)](https://github.com/Nycto/RBTreeNim/blob/master/LICENSE.md)



A Red/Black Tree implementation in Nim



Red/Black trees are self balancing binary search trees that maintain structure

by tracking an extra bit of state about each node. This is then used to examine

relationships between parents and children, allowing appropriate rotations to

be performed. See

[Wikipedia](http://en.wikipedia.org/wiki/Red%E2%80%93black_tree) for more info.



API Docs

--------



http://nycto.github.io/RBTreeNim/rbtree.html



A Quick Tour

------------



```nimrod

import rbtree



# Create a new tree

var tree = newRBTree[int, int]()



# Insert 4 values into the tree. Insert accepts 1 or more arguments to insert

tree.insert(2, 3, 1, 0)



# Remove one of those values

tree.delete(1)



# Check whether a value exists in the tree

if tree.contains(3):

    echo "Tree contains '3'"



# Iterate over every value in the tree

for i in tree:

    echo i



# Or iterate in reverse

for i in reversed(tree):

    echo i

```



Custom Keys

-----------



A Red/Black tree has a concept of a 'key' and a 'comparator'. When you call

`fetch`, the key is what you pass in. Sometimes this is the object itself, but

other times it's a derived value. When that is the case, you can define an

`extract` function that returns the key.



For example, if you are indexing X/Y coordinates by just the `x` value:



```nimrod

import rbtree



proc extract( point: tuple[x, y: int] ): int = point.x



var tree = newRBTree[tuple[x, y: int], int]()



tree.insert( (x: 234, y: 789) )

tree.insert( (x: 890, y: 123) )



echo tree.contains(234)

echo tree

```



Custom Comparators

------------------



Values are inserted into a Red/Black Tree in sorted order. The definition of

"sorted order", howerver, can be customized by defining a `cmp` function.

It should take two values, `(a, b)`, and returns `< 0` if `a < b`, `> 0` if

`a > b`, and `0` if `x == y`.



For example, if you wanted to sort a tree of coordinates by their `y` values:



```nimrod

import rbtree



type MyPoint = object

    x, y: int



proc cmp*( a, b: MyPoint ): int = cmp(a.y, b.y)



var tree = newRBTree[MyPoint, MyPoint]()



tree.insert( MyPoint(x: 234, y: 789) )

tree.insert( MyPoint(x: 890, y: 123) )



echo tree

```



Multiple Indexes

----------------



Sometimes you will want to index the same object in different ways. However,

this library uses compile time references to hook in the `extract` and `cmp`

methods. To get around this, you can define a custom `distinct` type that

will allow you to dispatch to different `extract` and `cmp` implementations.



```nimrod

import rbtree



# Define new types with custom extractors and comparators

defineIndex(XIndex, tuple[x, y: int], it.x, cmp(a, b))

defineIndex(YIndex, tuple[x, y: int], it.y, cmp(a, b))



var xIndex = newRBTree[XIndex, int]()

var yIndex = newRBTree[YIndex, int]()



let point1 = (x: 234, y: 789)

let point2 = (x: 890, y: 123)



xIndex.insert(point1, point2)

yIndex.insert(point1, point2)



echo xIndex

echo yIndex

```



License

-------



This library is released under the MIT License, which is pretty spiffy. You

should have received a copy of the MIT License along with this program. If

not, see http://www.opensource.org/licenses/mit-license.php