lean4-htt/src/Lean/ProjFns.lean
2025-12-09 15:47:54 +00:00

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/-
Copyright (c) 2019 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Leonardo de Moura
-/
module
prelude
public import Lean.EnvExtension
public section
namespace Lean
/--
Given a structure `S`, Lean automatically creates an auxiliary definition (projection function)
for each field. This structure caches information about these auxiliary definitions.
-/
structure ProjectionFunctionInfo where
/-- Constructor associated with the auxiliary projection function. -/
ctorName : Name
/-- Number of parameters in the structure -/
numParams : Nat
/-- The field index associated with the auxiliary projection function. -/
i : Nat
/-- `true` if the structure is a class. -/
fromClass : Bool
deriving Inhabited, Repr
@[export lean_mk_projection_info]
def mkProjectionInfoEx (ctorName : Name) (numParams : Nat) (i : Nat) (fromClass : Bool) : ProjectionFunctionInfo :=
{ ctorName, numParams, i, fromClass }
@[export lean_projection_info_from_class]
def ProjectionFunctionInfo.fromClassEx (info : ProjectionFunctionInfo) : Bool :=
info.fromClass
builtin_initialize projectionFnInfoExt : MapDeclarationExtension ProjectionFunctionInfo ← mkMapDeclarationExtension
def addProjectionFnInfo (env : Environment) (projName : Name) (ctorName : Name) (numParams : Nat) (i : Nat) (fromClass : Bool) : Environment :=
projectionFnInfoExt.insert env projName { ctorName, numParams, i, fromClass }
namespace Environment
def getProjectionFnInfo? (env : Environment) (projName : Name) : Option ProjectionFunctionInfo :=
projectionFnInfoExt.find? env projName
def isProjectionFn (env : Environment) (declName : Name) : Bool :=
projectionFnInfoExt.contains env declName
/-- If `projName` is the name of a projection function, return the associated structure name -/
def getProjectionStructureName? (env : Environment) (projName : Name) : Option Name :=
match env.getProjectionFnInfo? projName with
| none => none
| some projInfo =>
match env.find? projInfo.ctorName with
| some (ConstantInfo.ctorInfo val) => some val.induct
| _ => none
end Environment
def isProjectionFn [MonadEnv m] [Monad m] (declName : Name) : m Bool :=
return (← getEnv).isProjectionFn declName
def getProjectionFnInfo? [MonadEnv m] [Monad m] (declName : Name) : m (Option ProjectionFunctionInfo) :=
return (← getEnv).getProjectionFnInfo? declName
end Lean