| Copyright | Copyright (c) 1998 Chris Okasaki |
|---|---|
| License | BSD3; see COPYRIGHT file for terms and conditions |
| Maintainer | robdockins AT fastmail DOT fm |
| Stability | stable |
| Portability | GHC, Hugs (MPTC and FD) |
| Safe Haskell | Safe |
| Language | Haskell98 |
Data.Edison.Prelude
Contents
Description
This module is a central depository of common definitions used throughout Edison.
- class Eq a => Hash a where
- class Hash a => UniqueHash a
- class UniqueHash a => ReversibleHash a where
- class Monoid v => Measured v a | a -> v where
- measure :: a -> v
Hashing classes
class Eq a => Hash a where Source
This class represents hashable objects. If obeys the following invariant:
forall x,y :: a. (x == y) implies (hash x == hash y)
class Hash a => UniqueHash a Source
This class represents hashable objects where the hash function is unique (injective). There are no new methods, just a stronger invariant:
forall x,y :: a. (x == y) iff (hash x == hash y)
class UniqueHash a => ReversibleHash a where Source
This class represents hashable objects where the hash is reversible.
forall x :: a. unhash (hash x) == x
Note that:
hash (unhash i) == i
does not necessarily hold because unhash is not necessarily
defined for all i, only for all i in the range of hash.
class Monoid v => Measured v a | a -> v where Source
This class represents a quantity that can be measured. It is
calculated by an associative function with a unit (hence the
Monoid superclass, and by a function which gives the measurement
for an individual item. Some datastructures are able to speed up
the calculation of a measure by caching intermediate values of
the computation.