# critbits

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This module implements a crit bit tree which is an efficient container for a sorted set of strings, or for a sorted mapping of strings. Based on the excellent paper by Adam Langley. (A crit bit tree is a form of radix tree or patricia trie.)

Example:

    static:
      block:
        var critbitAsSet: CritBitTree[void]
        doAssert critbitAsSet.len == 0
        incl critbitAsSet, "kitten"
        doAssert critbitAsSet.len == 1
        incl critbitAsSet, "puppy"
        doAssert critbitAsSet.len == 2
        incl critbitAsSet, "kitten"
        doAssert critbitAsSet.len == 2
        incl critbitAsSet, ""
        doAssert critbitAsSet.len == 3
    block:
      var critbitAsDict: CritBitTree[int]
      critbitAsDict["key"] = 42
      doAssert critbitAsDict["key"] == 42
      critbitAsDict["key"] = 0
      doAssert critbitAsDict["key"] == 0
      critbitAsDict["key"] = -int.high
      doAssert critbitAsDict["key"] == -int.high
      critbitAsDict["key"] = int.high
      doAssert critbitAsDict["key"] == int.high

# Imports

since

# Types

    CritBitTree[T] = object
      root: Node[T]
      count: int

  The crit bit tree can either be used as a mapping from strings to some type `T` or as a set of strings if `T` is void. Source Edit

# Procs

    proc excl[T](c: var CritBitTree[T]; key: string)

  Removes `key` (and its associated value) from the set `c`. If the `key` does not exist, nothing happens.

  See also:

  - incl proc
  - incl proc

  Example:

      var c: CritBitTree[void]
      incl(c, "key")
      excl(c, "key")
      doAssert not c.contains("key")

  Source Edit

    proc missingOrExcl[T](c: var CritBitTree[T]; key: string): bool

  Returns true if `c` does not contain the given `key`. If the key does exist, c.excl(key) is performed.

  See also:

  - excl proc
  - containsOrIncl proc
  - containsOrIncl proc

  Example:

      block:
        var c: CritBitTree[void]
        doAssert c.missingOrExcl("key")
      block:
        var c: CritBitTree[void]
        incl(c, "key")
        doAssert not c.missingOrExcl("key")
        doAssert not c.contains("key")

  Source Edit

    proc containsOrIncl[T](c: var CritBitTree[T]; key: string; val: T): bool

  Returns true if `c` contains the given `key`. If the key does not exist `c[key] = val` is performed.

  See also:

  - incl proc
  - incl proc
  - containsOrIncl proc
  - missingOrExcl proc

  Example:

      block:
        var c: CritBitTree[int]
        doAssert not c.containsOrIncl("key", 42)
        doAssert c.contains("key")
      block:
        var c: CritBitTree[int]
        incl(c, "key", 21)
        doAssert c.containsOrIncl("key", 42)
        doAssert c["key"] == 21

  Source Edit

    proc containsOrIncl(c: var CritBitTree[void]; key: string): bool {...}{.raises: [],
        tags: [].}

  Returns true if `c` contains the given `key`. If the key does not exist it is inserted into `c`.

  See also:

  - incl proc
  - incl proc
  - containsOrIncl proc
  - missingOrExcl proc

  Example:

      block:
        var c: CritBitTree[void]
        doAssert not c.containsOrIncl("key")
        doAssert c.contains("key")
      block:
        var c: CritBitTree[void]
        incl(c, "key")
        doAssert c.containsOrIncl("key")

  Source Edit

    proc inc(c: var CritBitTree[int]; key: string; val: int = 1) {...}{.raises: [],
        tags: [].}

  Increments `c[key]` by `val`.

  Example:

      var c: CritBitTree[int]
      c["key"] = 1
      inc(c, "key")
      doAssert c["key"] == 2

  Source Edit

    proc incl(c: var CritBitTree[void]; key: string) {...}{.raises: [], tags: [].}

  Includes `key` in `c`.

  See also:

  - excl proc
  - incl proc

  Example:

      var c: CritBitTree[void]
      incl(c, "key")
      doAssert c.hasKey("key")

  Source Edit

    proc incl[T](c: var CritBitTree[T]; key: string; val: T)

  Inserts `key` with value `val` into `c`.

  See also:

  - excl proc
  - incl proc

  Example:

      var c: CritBitTree[int]
      incl(c, "key", 42)
      doAssert c["key"] == 42

  Source Edit

    proc `[]=`[T](c: var CritBitTree[T]; key: string; val: T)

  Puts a (key, value)-pair into `t`.

  See also:

  - [] proc
  - [] proc

  Example:

      var c: CritBitTree[int]
      c["key"] = 42
      doAssert c["key"] == 42

  Source Edit

# Funcs

    func len[T](c: CritBitTree[T]): int {...}{.inline.}

  Returns the number of elements in `c` in O(1).

  Example:

      var c: CritBitTree[void]
      incl(c, "key1")
      incl(c, "key2")
      doAssert c.len == 2

  Source Edit

    func contains[T](c: CritBitTree[T]; key: string): bool {...}{.inline.}

  Returns true if `c` contains the given `key`.

  Example:

      var c: CritBitTree[void]
      incl(c, "key")
      doAssert c.contains("key")

  Source Edit

    func hasKey[T](c: CritBitTree[T]; key: string): bool {...}{.inline.}

  Alias for contains. Source Edit

    func `[]`[T](c: CritBitTree[T]; key: string): T {...}{.inline.}

  Retrieves the value at `c[key]`. If `key` is not in `t`, the `KeyError` exception is raised. One can check with `hasKey` whether the key exists.

  See also:

  - [] proc
  - []= proc
  Source Edit

    func `[]`[T](c: var CritBitTree[T]; key: string): var T {...}{.inline.}

  Retrieves the value at `c[key]`. The value can be modified. If `key` is not in `t`, the `KeyError` exception is raised.

  See also:

  - [] proc
  - []= proc
  Source Edit

    func `$`[T](c: CritBitTree[T]): string

  Turns `c` into a string representation. Example outputs: `{keyA: value, keyB: value}`, `{:}` If `T` is void the outputs look like: `{keyA, keyB}`, `{}`. Source Edit

    func commonPrefixLen[T](c: CritBitTree[T]): int {...}{.inline.}

  Returns longest common prefix length of all keys of `c`. If `c` is empty, returns 0.

  Example:

      var c: CritBitTree[void]
      doAssert c.commonPrefixLen == 0
      incl(c, "key1")
      doAssert c.commonPrefixLen == 4
      incl(c, "key2")
      doAssert c.commonPrefixLen == 3

  Source Edit

    func toCritBitTree[A, B](pairs: openArray[(A, B)]): CritBitTree[A]

  Creates a new `CritBitTree` that contains the given `pairs`.

  Example:

      doAssert {"a": "0", "b": "1", "c": "2"}.toCritBitTree is CritBitTree[string]

  Source Edit

    func toCritBitTree[T](items: openArray[T]): CritBitTree[void]

  Creates a new `CritBitTree` that contains the given `items`.

  Example:

      doAssert ["a", "b", "c"].toCritBitTree is CritBitTree[void]

  Source Edit

# Iterators

    iterator keys[T](c: CritBitTree[T]): string

  Yields all keys in lexicographical order.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 1
      c["key2"] = 2
      var keys: seq[string]
      for key in c.keys:
        keys.add(key)
      doAssert keys == @["key1", "key2"]

  Source Edit

    iterator values[T](c: CritBitTree[T]): T

  Yields all values of `c` in the lexicographical order of the corresponding keys.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 1
      c["key2"] = 2
      var vals: seq[int]
      for val in c.values:
        vals.add(val)
      doAssert vals == @[1, 2]

  Source Edit

    iterator mvalues[T](c: var CritBitTree[T]): var T

  Yields all values of `c` in the lexicographical order of the corresponding keys. The values can be modified.

  See also:

  - values iterator
  Source Edit

    iterator items[T](c: CritBitTree[T]): string

  Yields all keys in lexicographical order.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 1
      c["key2"] = 2
      var keys: seq[string]
      for key in c.items:
        keys.add(key)
      doAssert keys == @["key1", "key2"]

  Source Edit

    iterator pairs[T](c: CritBitTree[T]): tuple[key: string, val: T]

  Yields all (key, value)-pairs of `c`.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 1
      c["key2"] = 2
      var ps: seq[tuple[key: string, val: int]]
      for p in c.pairs:
        ps.add(p)
      doAssert ps == @[(key: "key1", val: 1), (key: "key2", val: 2)]

  Source Edit

    iterator mpairs[T](c: var CritBitTree[T]): tuple[key: string, val: var T]

  Yields all (key, value)-pairs of `c`. The yielded values can be modified.

  See also:

  - pairs iterator
  Source Edit

    iterator itemsWithPrefix[T](c: CritBitTree[T]; prefix: string;
                                longestMatch = false): string

  Yields all keys starting with `prefix`. If `longestMatch` is true, the longest match is returned, it doesn't have to be a complete match then.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 42
      c["key2"] = 43
      var keys: seq[string]
      for key in c.itemsWithPrefix("key"):
        keys.add(key)
      doAssert keys == @["key1", "key2"]

  Source Edit

    iterator keysWithPrefix[T](c: CritBitTree[T]; prefix: string;
                               longestMatch = false): string

  Yields all keys starting with `prefix`.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 42
      c["key2"] = 43
      var keys: seq[string]
      for key in c.keysWithPrefix("key"):
        keys.add(key)
      doAssert keys == @["key1", "key2"]

  Source Edit

    iterator valuesWithPrefix[T](c: CritBitTree[T]; prefix: string;
                                 longestMatch = false): T

  Yields all values of `c` starting with `prefix` of the corresponding keys.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 42
      c["key2"] = 43
      var vals: seq[int]
      for val in c.valuesWithPrefix("key"):
        vals.add(val)
      doAssert vals == @[42, 43]

  Source Edit

    iterator mvaluesWithPrefix[T](c: var CritBitTree[T]; prefix: string;
                                  longestMatch = false): var T

  Yields all values of `c` starting with `prefix` of the corresponding keys. The values can be modified.

  See also:

  - valuesWithPrefix iterator
  Source Edit

    iterator pairsWithPrefix[T](c: CritBitTree[T]; prefix: string;
                                longestMatch = false): tuple[key: string, val: T]

  Yields all (key, value)-pairs of `c` starting with `prefix`.

  Example:

      var c: CritBitTree[int]
      c["key1"] = 42
      c["key2"] = 43
      var ps: seq[tuple[key: string, val: int]]
      for p in c.pairsWithPrefix("key"):
        ps.add(p)
      doAssert ps == @[(key: "key1", val: 42), (key: "key2", val: 43)]

  Source Edit

    iterator mpairsWithPrefix[T](c: var CritBitTree[T]; prefix: string;
                                 longestMatch = false): tuple[key: string,
        val: var T]

  Yields all (key, value)-pairs of `c` starting with `prefix`. The yielded values can be modified.

  See also:

  - pairsWithPrefix iterator
  Source Edit