Portability	non-portable (GHC-specific)
Stability	experimental
Maintainer	http://www.cse.chalmers.se/~nad/
Safe Haskell	None

Test.ChasingBottoms.SemanticOrd

Description

Generic semantic equality and order. The semantic order referred to is that of a typical CPO for Haskell types, where e.g. (True, bottom) <=! (True, False), but where (True, True) and (True, False) are incomparable.

The implementation is based on isBottom, and has the same limitations. Note that non-bottom functions are not handled by any of the functions described below.

One could imagine using QuickCheck for testing equality of functions, but I have not managed to tweak the type system so that it can be done transparently.

Synopsis

Documentation

data Tweak Source

The behaviour of some of the functions below can be tweaked.

Constructors

Tweak
Fields approxDepth :: Maybe Nat If equal to `Just n`, an `approxAll n` is performed on all arguments before doing whatever the function is supposed to be doing. timeOutLimit :: Maybe Int If equal to `Just n`, then all computations that take more than `n` seconds to complete are considered to be equal to `bottom`. This functionality is implemented using `isBottomTimeOut`.

Instances

Eq Tweak
Ord Tweak
Show Tweak

noTweak :: Tweak Source

No tweak (both fields are Nothing).

class SemanticEq a whereSource

SemanticEq contains methods for testing whether two terms are semantically equal.

Methods

(==!), (/=!) :: a -> a -> Bool Source

semanticEq :: Tweak -> a -> a -> Bool Source

Instances

Data a => SemanticEq a

class SemanticEq a => SemanticOrd a whereSource

SemanticOrd contains methods for testing whether two terms are related according to the semantic domain ordering.

Methods

(<!), (>!), (>=!), (<=!) :: a -> a -> Bool Source

semanticCompare :: Tweak -> a -> a -> Maybe Ordering Source

semanticCompare tweak x y returns Nothing if x and y are incomparable, and Just o otherwise, where o :: Ordering represents the relation between x and y.

(\/!) :: a -> a -> Maybe aSource

(/\!) :: a -> a -> aSource

semanticJoin :: Tweak -> a -> a -> Maybe aSource

semanticMeet :: Tweak -> a -> a -> aSource

x \/! y and x /\! y compute the least upper and greatest lower bounds, respectively, of x and y in the semantical domain ordering. Note that the least upper bound may not always exist. This functionality was implemented just because it was possible (and to provide analogues of max and min in the Ord class). If anyone finds any use for it, please let me know.

Instances

(SemanticEq a, Data a) => SemanticOrd a