ghc-6.10.2: The GHC APIContentsIndex
CoreSubst
Contents
Main data types
Substituting into expressions and related types
Operations on substitutions
Substituting and cloning binders
Synopsis
data Subst
type TvSubstEnv = TyVarEnv Type
type IdSubstEnv = IdEnv CoreExpr
data InScopeSet
deShadowBinds :: [CoreBind] -> [CoreBind]
substTy :: Subst -> Type -> Type
substExpr :: Subst -> CoreExpr -> CoreExpr
substSpec :: Subst -> Id -> SpecInfo -> SpecInfo
substWorker :: Subst -> WorkerInfo -> WorkerInfo
lookupIdSubst :: Subst -> Id -> CoreExpr
lookupTvSubst :: Subst -> TyVar -> Type
emptySubst :: Subst
mkEmptySubst :: InScopeSet -> Subst
mkSubst :: InScopeSet -> TvSubstEnv -> IdSubstEnv -> Subst
substInScope :: Subst -> InScopeSet
isEmptySubst :: Subst -> Bool
extendIdSubst :: Subst -> Id -> CoreExpr -> Subst
extendIdSubstList :: Subst -> [(Id, CoreExpr)] -> Subst
extendTvSubst :: Subst -> TyVar -> Type -> Subst
extendTvSubstList :: Subst -> [(TyVar, Type)] -> Subst
extendSubst :: Subst -> Var -> CoreArg -> Subst
extendSubstList :: Subst -> [(Var, CoreArg)] -> Subst
zapSubstEnv :: Subst -> Subst
extendInScope :: Subst -> Var -> Subst
extendInScopeList :: Subst -> [Var] -> Subst
extendInScopeIds :: Subst -> [Id] -> Subst
isInScope :: Var -> Subst -> Bool
substBndr :: Subst -> Var -> (Subst, Var)
substBndrs :: Subst -> [Var] -> (Subst, [Var])
substRecBndrs :: Subst -> [Id] -> (Subst, [Id])
cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id)
cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
cloneRecIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
Main data types
data Subst

A substitution environment, containing both Id and TyVar substitutions.

Some invariants apply to how you use the substitution:

1. The in-scope set contains at least those Ids and TyVars that will be in scope after applying the substitution to a term. Precisely, the in-scope set must be a superset of the free vars of the substitution range that might possibly clash with locally-bound variables in the thing being substituted in.

2. You may apply the substitution only once

There are various ways of setting up the in-scope set such that the first of these invariants hold:

  • Arrange that the in-scope set really is all the things in scope
  • Arrange that it's the free vars of the range of the substitution
  • Make it empty, if you know that all the free vars of the substitution are fresh, and hence can't possibly clash
show/hide Instances
type TvSubstEnv = TyVarEnv Type
A substitition of Types for TyVars
type IdSubstEnv = IdEnv CoreExpr
An environment for substituting for Ids
data InScopeSet
A set of variables that are in scope at some point
show/hide Instances
Substituting into expressions and related types
deShadowBinds :: [CoreBind] -> [CoreBind]

De-shadowing the program is sometimes a useful pre-pass. It can be done simply by running over the bindings with an empty substitution, becuase substitution returns a result that has no-shadowing guaranteed.

(Actually, within a single type there might still be shadowing, because substTy is a no-op for the empty substitution, but that's probably OK.)

substTy :: Subst -> Type -> Type
See substTy
substExpr :: Subst -> CoreExpr -> CoreExpr

Apply a substititon to an entire CoreExpr. Rememeber, you may only apply the substitution once: see CoreSubst

Do *not* attempt to short-cut in the case of an empty substitution! See Note [Extending the Subst]

substSpec :: Subst -> Id -> SpecInfo -> SpecInfo
Substitutes for the Ids within the WorkerInfo given the new function Id
substWorker :: Subst -> WorkerInfo -> WorkerInfo
Substitutes for the Ids within the WorkerInfo
lookupIdSubst :: Subst -> Id -> CoreExpr
Find the substitution for an Id in the Subst
lookupTvSubst :: Subst -> TyVar -> Type
Find the substitution for a TyVar in the Subst
Operations on substitutions
emptySubst :: Subst
mkEmptySubst :: InScopeSet -> Subst
mkSubst :: InScopeSet -> TvSubstEnv -> IdSubstEnv -> Subst
substInScope :: Subst -> InScopeSet
Find the in-scope set: see CoreSubst
isEmptySubst :: Subst -> Bool
extendIdSubst :: Subst -> Id -> CoreExpr -> Subst
Add a substitution for an Id to the Subst: you must ensure that the in-scope set is such that the CoreSubst is true after extending the substitution like this
extendIdSubstList :: Subst -> [(Id, CoreExpr)] -> Subst
Adds multiple Id substitutions to the Subst: see also extendIdSubst
extendTvSubst :: Subst -> TyVar -> Type -> Subst
Add a substitution for a TyVar to the Subst: you must ensure that the in-scope set is such that the CoreSubst is true after extending the substitution like this
extendTvSubstList :: Subst -> [(TyVar, Type)] -> Subst
Adds multiple TyVar substitutions to the Subst: see also extendTvSubst
extendSubst :: Subst -> Var -> CoreArg -> Subst
Add a substitution for a TyVar or Id as appropriate to the Var being added. See also extendIdSubst and extendTvSubst
extendSubstList :: Subst -> [(Var, CoreArg)] -> Subst
Add a substitution for a TyVar or Id as appropriate to all the Vars being added. See also extendSubst
zapSubstEnv :: Subst -> Subst
Remove all substitutions for Ids and Vars that might have been built up while preserving the in-scope set
extendInScope :: Subst -> Var -> Subst
Add the Var to the in-scope set: as a side effect, removes any existing substitutions for it
extendInScopeList :: Subst -> [Var] -> Subst
Add the Vars to the in-scope set: see also extendInScope
extendInScopeIds :: Subst -> [Id] -> Subst
Optimized version of extendInScopeList that can be used if you are certain all the things being added are Ids and hence none are TyVars
isInScope :: Var -> Subst -> Bool
Substituting and cloning binders
substBndr :: Subst -> Var -> (Subst, Var)
Substitutes a Var for another one according to the Subst given, returning the result and an updated Subst that should be used by subsequent substitutons. IdInfo is preserved by this process, although it is substituted into appropriately.
substBndrs :: Subst -> [Var] -> (Subst, [Var])
Applies substBndr to a number of Vars, accumulating a new Subst left-to-right
substRecBndrs :: Subst -> [Id] -> (Subst, [Id])
Substitute in a mutually recursive group of Ids
cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id)
Very similar to substBndr, but it always allocates a new Unique for each variable in its output and removes all IdInfo
cloneIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
Applies cloneIdBndr to a number of Ids, accumulating a final substitution from left to right
cloneRecIdBndrs :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
Clone a mutually recursive group of Ids
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