Module hashes

This module implements efficient computations of hash values for diverse Nim types. All the procs are based on these two building blocks: the !& proc used to start or mix a hash value, and the !$ proc used to finish the hash value. If you want to implement hash procs for your custom types you will end up writing the following kind of skeleton of code:

proc hash(x: Something): THash =
  ## Computes a THash from `x`.
  var h: THash = 0
  # Iterate over parts of `x`.
  for xAtom in x:
    # Mix the atom with the partial hash.
    h = h !& xAtom
  # Finish the hash.
  result = !$h

If your custom types contain fields for which there already is a hash proc, like for example objects made up of strings, you can simply hash together the hash value of the individual fields:

proc hash(x: Something): THash =
  ## Computes a THash from `x`.
  var h: THash = 0
  h = h !& hash(x.foo)
  h = h !& hash(x.bar)
  result = !$h

Types

THash = int
a hash value; hash tables using these values should always have a size of a power of two and can use the and operator instead of mod for truncation of the hash value.   Source

Procs

proc `!&`(h: THash; val: int): THash {.inline, raises: [], tags: [].}
mixes a hash value h with val to produce a new hash value. This is only needed if you need to implement a hash proc for a new datatype.   Source
proc `!$`(h: THash): THash {.inline, raises: [], tags: [].}
finishes the computation of the hash value. This is only needed if you need to implement a hash proc for a new datatype.   Source
proc hashData(data: pointer; size: int): THash {.raises: [], tags: [].}
hashes an array of bytes of size size   Source
proc hash(x: pointer): THash {.inline, raises: [], tags: [].}
efficient hashing of pointers   Source
proc hash[T](x: T): THash {.inline.}
efficient hashing of proc vars; closures are supported too.   Source
proc hash(x: int): THash {.inline, raises: [], tags: [].}
efficient hashing of integers   Source
proc hash(x: int64): THash {.inline, raises: [], tags: [].}
efficient hashing of integers   Source
proc hash(x: char): THash {.inline, raises: [], tags: [].}
efficient hashing of characters   Source
proc hash(x: string): THash {.raises: [], tags: [].}
efficient hashing of strings   Source
proc hashIgnoreStyle(x: string): THash {.raises: [], tags: [].}
efficient hashing of strings; style is ignored   Source
proc hashIgnoreCase(x: string): THash {.raises: [], tags: [].}
efficient hashing of strings; case is ignored   Source
proc hash[T](x: T): THash
efficient hashing of tuples.   Source
proc hash(x: float): THash {.inline, raises: [], tags: [].}
  Source
proc hash[A](x: openArray[A]): THash
  Source
proc hash[A](x: set[A]): THash
  Source