package registry

// An Expr is a type-erased lambda calculus expression. It can have any type of
// representation, so long as that type is known to the registry it is handled
// by.
type Expr interface {
	// Repr returns the name of the underlying representation. Two expressions
	// with the same Repr() are assumed to have the same representation type.
	Repr() string

	// Data returns the underlying expression data.
	Data() any
}

// A baseExpr is the default implementation of Expr.
type baseExpr struct {
	id   string
	data any
}

func (e baseExpr) Repr() string { return e.id }

func (e baseExpr) Data() any { return e.data }

// NewExpr creates an Expr with the given representation name and data.
func NewExpr(id string, data any) Expr { return baseExpr{id, data} }