     }
 }
 
-public struct BoolLiteralExpression : ValueExpression, RValueExpression {
+public struct BoolLiteralExpression : LiteralExpression {
     public typealias ValueType = Bool
     
     public let hashValue: Int = nextHashValue()

    }
}

public struct StringLiteralExpression : ValueExpression, RValueExpression {
    public typealias ValueType = String
    
    public let hashValue: Int = nextHashValue()

    }
}

public struct RealLiteralExpression : LiteralExpression {
    public typealias ValueType = Double
    
    public let hashValue: Int = nextHashValue()
