promql/engine.go
func scalarBinop(op ItemType, lhs, rhs float64) float64 {
	switch op {
	case ItemADD:
		return lhs + rhs
	case ItemSUB:
		return lhs - rhs
	case ItemMUL:
		return lhs * rhs
	case ItemDIV:
		return lhs / rhs
	case ItemPOW:
		return math.Pow(lhs, rhs)
	case ItemMOD:
		return math.Mod(lhs, rhs)
	case ItemEQL:
		return btos(lhs == rhs)
	case ItemNEQ:
		return btos(lhs != rhs)
	case ItemGTR:
		return btos(lhs > rhs)
	case ItemLSS:
		return btos(lhs < rhs)
	case ItemGTE:
		return btos(lhs >= rhs)
	case ItemLTE:
		return btos(lhs <= rhs)
	}
	panic(errors.Errorf("operator %q not allowed for Scalar operations", op))
}
func scalarBinop(op ItemType, lhs, rhs float64) float64 {
	switch op {
	case ItemADD:
		return lhs + rhs
	case ItemSUB:
		return lhs - rhs
	case ItemMUL:
		return lhs * rhs
	case ItemDIV:
		return lhs / rhs
	case ItemPOW:
		return math.Pow(lhs, rhs)
	case ItemMOD:
		return math.Mod(lhs, rhs)
	case ItemEQL:
		return btos(lhs == rhs)
	case ItemNEQ:
		return btos(lhs != rhs)
	case ItemGTR:
		return btos(lhs > rhs)
	case ItemLSS:
		return btos(lhs < rhs)
	case ItemGTE:
		return btos(lhs >= rhs)
	case ItemLTE:
		return btos(lhs <= rhs)
	}
	panic(errors.Errorf("operator %q not allowed for Scalar operations", op))
}
// scalarBinop evaluates a binary operation between two Scalars.