UniqueLogic.ST.Expression

Documentation

data T s a

An expression is defined by a set of equations and the variable at the top-level. The value of the expression equals the value of the top variable.

Instances

Fractional a => Fractional (T s a)

Fractional a => Num (T s a)

Construct primitive expressions

constant :: a -> T s a

Make a constant expression of a simple numeric value.

fromVariable :: Variable s a -> T s a

Operators from rules with small numbers of arguments

fromRule1 :: (Variable s a -> M s ()) -> T s a

fromRule2 :: (Variable s a -> Variable s b -> M s ()) -> T s a -> T s b

fromRule3 :: (Variable s a -> Variable s b -> Variable s c -> M s ()) -> T s a -> T s b -> T s c

Operators from rules with any number of arguments

data Apply s f

Instances

Functor (Apply s)

Applicative (Apply s)

arg :: T s a -> Apply s (Variable s a)

This function allows to generalize fromRule2 and fromRule3 to more arguments using Applicative combinators.

Example:

 fromRule3 rule x y
    = runApply $ liftA2 rule (arg x) (arg y)
    = runApply $ pure rule <*> arg x <*> arg y

Building rules with arg provides more granularity than using auxiliary pair rules!

runApply :: Apply s (Variable s a -> M s ()) -> T s a

Predicates on expressions

(=:=) :: Eq a => T s a -> T s a -> M s ()

Common operators (see also Num and Fractional instances)

(=!=) :: Eq a => T s a -> T s a -> T s a

sqr :: Floating a => T s a -> T s a

sqrt :: Floating a => T s a -> T s a

max :: Ord a => T s a -> T s a -> T s a

We are not able to implement a full Ord instance including Eq superclass and comparisons, but we need to compute maxima.

maximum :: Ord a => [T s a] -> T s a

pair :: T s a -> T s b -> T s (a, b)

Construct or decompose a pair.