inductive Lean.HeadIndex : Type

• fvar: Lean.FVarId → Lean.HeadIndex
• mvar: Lean.MVarId → Lean.HeadIndex
• const: Lake.Name → Lean.HeadIndex
• proj: Lake.Name → Nat → Lean.HeadIndex
• lit: Lean.Literal → Lean.HeadIndex
• sort: Lean.HeadIndex
• lam: Lean.HeadIndex
• forallE: Lean.HeadIndex

Datastructure for representing the "head symbol" of an expression. It is the key of KExprMap. Examples:

• The head of f a is .const f
• The head of let x := 1; f x is .const f
• The head of fun x => fun is .lam

HeadIndex is a very simple index, and is used in situations where we want to find definitionally equal terms, but we want to minimize the search by checking only pairs of terms that have the same HeadIndex.

instance Lean.instInhabitedHeadIndex : Inhabited Lean.HeadIndex

instance Lean.instBEqHeadIndex : BEq Lean.HeadIndex

instance Lean.instReprHeadIndex : Repr Lean.HeadIndex

def Lean.HeadIndex.HeadIndex.hash : Lean.HeadIndex → UInt64

Hash code for a HeadIndex value.

instance Lean.HeadIndex.instHashableHeadIndex : Hashable Lean.HeadIndex

def Lean.Expr.headNumArgs (e : Lean.Expr) : Nat

Return the number of arguments in the given expression with respect to its HeadIndex

def Lean.Expr.headNumArgs.go : Lean.Expr → Nat → Nat

Equations

• Lean.Expr.headNumArgs.go (Lean.Expr.app f arg) x = Lean.Expr.headNumArgs.go f (x + 1)
• Lean.Expr.headNumArgs.go (Lean.Expr.letE declName type value b nonDep) x = Lean.Expr.headNumArgs.go b x
• Lean.Expr.headNumArgs.go (Lean.Expr.mdata data e) x = Lean.Expr.headNumArgs.go e x
• Lean.Expr.headNumArgs.go x x = x

def Lean.Expr.toHeadIndex (e : Lean.Expr) : Lean.HeadIndex

Convert the given expression into a HeadIndex.