Data.Scope

Lexical scope resolution over branded names: a spelling-to-binder stack.

While resolving syntax, a scope maps each source spelling to the stack of Data.Name binders currently in force for it. Entering a binding pushes; leaving pops; a reference resolves to the innermost binder. Shadowing is a push that changes what the spelling means without disturbing the identity underneath, so alpha-renaming a source program never changes which identities the resolved output carries, only their hints.

Failure is explicit and named: resolving an unknown spelling and popping a spelling with no active binder are ScopeError values, never silent fallbacks. The scope is an ordinary persistent value, so a resolver may thread it through State, pass it as an argument, or keep sub-scopes by simply keeping the old value. Opt-in: not in Base.

Types

`Scope`

type Scope(space) = Scope { spellings: Map(String, List(Binder(space))) }

A resolution scope for one namespace: each spelling maps to its stack of active binders, innermost first.

`ScopeError`

type ScopeError
  = ScopeUnknown(String)
  | ScopeUnderflow(String)
  deriving (Eq, Show)

Why a scope operation refused.

Functions and Values

`scope_empty`

scope_empty : forall a. Data.Scope.Scope(a)

The empty scope: no spelling resolves.

`scope_push`

scope_push : forall a. (Data.Scope.Scope(a), Data.Name.Binder(a)) -> Data.Scope.Scope(a)

Bring binder into force for its own hint spelling, shadowing any binder already in force for it.

`scope_lookup`

scope_lookup : forall a. (Data.Scope.Scope(a), String) -> Result(Data.Name.Binder(a), Data.Scope.ScopeError)

The innermost binder in force for spelling, or ScopeUnknown.

`scope_pop`

scope_pop : forall a. (Data.Scope.Scope(a), String) -> Result(Data.Scope.Scope(a), Data.Scope.ScopeError)

Leave the innermost binding for spelling, restoring whatever it shadowed; popping a spelling with no active binder is ScopeUnderflow.

`scope_depth`

scope_depth : forall a. (Data.Scope.Scope(a), String) -> Int

How many binders are in force for spelling; zero for an unknown one.

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