and (|Statement|_|) tokens =
        match tokens with
        | Token.Keyword ("let",row,col) :: remainingTokens ->
            match remainingTokens with
            | IdentifierDefinition (remainingTokens,identifier) ->
                let rec accumulateParameters tokens parameters =
                    match tokens with
                    | IdentifierDefinition (remainingTokens,identifier) ->
                        let parameters = parameters @ [identifier]
                        accumulateParameters remainingTokens parameters
                    | Token.Op (symbol,row,col) :: tail when symbol = "=" ->
                        (remainingTokens,parameters)
                    | token :: tail ->
                        let row,col = ((token :> IToken).row,(token :> IToken).col)
                        failwith <| errorMessage codeLines.[row] row col "Unexpected token in function declaration"
                    | _ -> failwith "Unexpected end of file"
                let (remainingTokens,parameters) = accumulateParameters remainingTokens []
                match parameters with
                | [] ->         //Value definition
                    match remainingTokens with
                    | Expression (remainingTokens,expression) ->
                        Some (remainingTokens,ValueDefinition (identifier,expression))
                    | token :: tail ->
                        let row,col = ((token :> IToken).row,(token :> IToken).col)
                        failwith <| errorMessage codeLines.[row] row col "Expected expression"
                    | _ -> failwith "Unexpected end of file"
                | parameters -> //Function definition
                    match remainingTokens with
                    | Expression (remainingTokens,expression) ->
                        Some (remainingTokens,FunctionDefinition (identifier,parameters,expression))
                    | token :: tail ->
                        let row,col = ((token :> IToken).row,(token :> IToken).col)
                        failwith <| errorMessage codeLines.[row] row col "Expected expression"
                    | _ -> failwith "Unexpected end of file"
            | token :: tail ->
                let row,col = ((token :> IToken).row,(token :> IToken).col)
                failwith <| errorMessage codeLines.[row] row col "Unexpected token after let"
            | _ -> failwith "Unexpected end of file"
        | _ -> None