variable.go

// Copyright 2020-2025 Consensys Software Inc.
// Licensed under the Apache License, Version 2.0. See the LICENSE file for details.

package frontend

import (
	"github.com/consensys/gnark/frontend/internal/expr"
)

// Variable represents a variable in the circuit. Any integer type (e.g. int, *big.Int, fr.Element)
// can be assigned to it. It is also allowed to set a base-10 encoded string representing an integer value.
// The only purpose of putting this definition here is to avoid the import cycles (cs/plonk <-> frontend) and (cs/r1cs <-> frontend)
type Variable interface{}

// IsCanonical returns true if the Variable has been normalized in a (internal) LinearExpression
// by one of the constraint system builders. In other words, if the Variable is a circuit input OR
// returned by the API.
func IsCanonical(v Variable) bool {
	switch v.(type) {
	case expr.LinearExpression, *expr.LinearExpression, expr.Term, *expr.Term:
		return true
	}
	return false
}