Copyright	(C) 2012-2016 University of Twente 2021 QBayLogic B.V.
License	BSD2 (see the file LICENSE)
Maintainer	QBayLogic B.V. <devops@qbaylogic.com>
Safe Haskell	None
Language	Haskell2010

Clash.Core.FreeVars

Contents

Free variable calculation
occurrence check
Internal

Description

Free variable calculations

Synopsis

typeFreeVars :: Fold Type TyVar
freeIds :: Fold Term Id
freeLocalVars :: Fold Term (Var a)
freeLocalIds :: Fold Term Id
globalIds :: Fold Term Id
termFreeTyVars :: Fold Term TyVar
globalIdOccursIn :: Id -> Term -> Bool
localVarsDoNotOccurIn :: [Var a] -> Term -> Bool
countFreeOccurances :: Term -> VarEnv Int
typeFreeVars' :: (Contravariant f, Applicative f) => (forall b. Var b -> Bool) -> IntSet -> (Var a -> f (Var a)) -> Type -> f Type
termFreeVars' :: (Contravariant f, Applicative f) => (forall b. Var b -> Bool) -> (Var a -> f (Var a)) -> Term -> f Term

Free variable calculation

typeFreeVars :: Fold Type TyVar Source #

Gives the free type-variables in a Type, implemented as a Fold

The Fold is closed over the types of its variables, so:

foldMapOf typeFreeVars unitVarSet ((a:* -> k) Int) = {a, k}

freeIds :: Fold Term Id Source #

Gives the free identifiers of a Term, implemented as a Fold

freeLocalVars :: Fold Term (Var a) Source #

Calculate the local free variable of an expression: the free type variables and the free identifiers that are not bound in the global environment.

freeLocalIds :: Fold Term Id Source #

Calculate the local free identifiers of an expression: the free identifiers that are not bound in the global environment.

globalIds :: Fold Term Id Source #

Calculate the global free identifiers of an expression: the free identifiers that are bound in the global environment.

termFreeTyVars :: Fold Term TyVar Source #

Gives the free type-variables of a Term, implemented as a Fold

The Fold is closed over the types of variables, so:

foldMapOf termFreeTyVars unitVarSet (case (x : (a:* -> k) Int)) of {}) = {a, k}

occurrence check

globalIdOccursIn :: Id -> Term -> Bool Source #

Check whether a local identifier occurs free in a term

localVarsDoNotOccurIn :: [Var a] -> Term -> Bool Source #

Check whether a set of variables does not occur free in a term

countFreeOccurances :: Term -> VarEnv Int Source #

Get the free variables of an expression and count the number of occurrences

Internal

typeFreeVars' Source #

Arguments

:: (Contravariant f, Applicative f)
=> (forall b. Var b -> Bool)	Predicate telling whether a variable is interesting
-> IntSet	Uniques of the variables in scope, used by `termFreeVars'`
-> (Var a -> f (Var a))
-> Type
-> f Type

Gives the "interesting" free variables in a Type, implemented as a Fold

The Fold is closed over the types of variables, so:

foldMapOf (typeFreeVars' (const True) IntSet.empty) unitVarSet ((a:* -> k) Int) = {a, k}

Note [Closing over kind variables]

Consider the type

forall k . b -> k

where

b :: k -> Type

When we close over the free variables of forall k . b -> k, i.e. b, then the k in b :: k -> Type is most definitely not the k in forall k . b -> k. So when a type variable is free, i.e. not in the inScope set, its kind variables also aren´t; so in order to prevent collisions due to shadowing we close using an empty inScope set.

termFreeVars' Source #

Arguments

:: (Contravariant f, Applicative f)
=> (forall b. Var b -> Bool)	Predicate telling whether a variable is interesting
-> (Var a -> f (Var a))
-> Term
-> f Term

Gives the "interesting" free variables in a Term, implemented as a Fold

The Fold is closed over the types of variables, so:

foldMapOf (termFreeVars' (const True)) unitVarSet (case (x : (a:* -> k) Int)) of {}) = {x, a, k}

Note [Closing over type variables]

Consider the term

/\(k :: Type) -> \(b :: k) -> a

where

a :: k

When we close over the free variables of /k -> (b :: k) -> (a :: k), i.e. a, then the k in a :: k is most definitely not the k in introduced by the /k ->. So when a term variable is free, i.e. not in the inScope set, its type variables also aren´t; so in order to prevent collisions due to shadowing we close using an empty inScope set.