Please help fix this code and add anything to it so that it is not limited:

Please use the following grammar:

prog $->$ begin stmt$\_$list end

stmt$\_$list $->$ stmt ; stmt$\_$list

$|$ stmt

$|$ stmt ;

stmt $->$ var $=$ expr

var $->$ A $|$ B $|$ C

expr $->$ var $+$ expr

$|$ var $-$ expr

$|$ var

Implement a recursive descent parser.

Note that:

$-$ we have two keywords: begin and end

$-$ we have only three valid identifier: A$,$ B$,$ and C

$-$ the grammar supports three operators: $=,+,$ and $-$

$-$ a semicolon $($;$)$ is a stmt separator within stmt$\_$list

The lexical analyzer in lexan.cpp has already been modified to recognize the tokens listed

above. You may want to compile and run test$-$lexan.cpp with lexan.cpp to verify that this

is the case. Use the input file tp$-01.$txt and create others that you find necessary. It does

not mean that any token that the lexical analyzer recognizes is a valid token for the prog

grammar above. It is the parser's job to flag invalid input due to bad tokens or invalid

statements.

Here are three examples of valid input files $($they appear in parser.zip and they are tp$-$

$01.$txt$,$ tp$-02.$txt$,$ and tp$-03.$txt$)$:

$1)$ begin

A $=$ A

end

$2)$ begin

A $=$ A;

B $=$ C

end

$3)$ begin

B $=$ A $+$ C;

A $=$ B;

C $=$ A $-$ B $+$ C $-$ A;

end

The results appear in the file out$-01.$txt$,$ out$-02.$txt$,$ and out$-03.$txt

Remember, if we can generate a parse tree for an input file, your parser should accept the

input. Anything else should be flagged as an error.

code should not be limited to handle only these three examples

Code: #include

#include

#include

#include "token.h

$"$

#include "functions.h

$"$

using namespace std;

ifstream ifs;

$//$

$$input file stream used by lexan

SymTab symtab;

$//$

$$global symbol table

Token token;

$//$

$$global token

int lookahead

$=$

$0$

;

$//$

$$no look ahead token yet

int dbg

$=$

$1$

;

$//$

$$debut is ON

int main

$()$

$\{$

ifs

$=$

$$get

$\_$

ifs

$()$

;

$//$

$$open an input file stream w

$/$

$$the program

init

$\_$

kws

$()$

;

$//$

$$initialize keywords in the symtab

match

$($

$$lookahead

$)$

;

$//$

$$get the first input token

prog

$()$

;

return

$0$

;

$\}$

$/*$

prog

$-$

$>$

$$begin stmt

$\_$

list end

stmt

$\_$

list

$-$

$>$

$$stmt ; stmt

$\_$

list

$|$

$$stmt

$|$

$$stmt;

stmt

$-$

$>$

$$var

$=$

$$expr

var

$-$

$>$

$$A

$|$

$$B

$|$

$$C

expr

$-$

$>$

$$var

$+$

$$expr

$|$

$$var

$-$

$$expr

$|$

$$var

$*/$

void begin

$()$

$\{$

match

$($

$$KW

$)$

;

$\}$

void end

$()$

$\{$

match

$($

$$KW

$)$

;

$\}$

void stmts

$()$

$\{$

stmt

$()$

;

if

$($

$$lookahead

$=$

$=$

$\text{'}$

;

$\text{'})$

$\{$

match

$(\text{'}$

;

$\text{'})$

;

stmts

$()$

;

$\}$

$\}$

void stmt

$()$

$\{$

var

$()$

;

match

$(\text{'}$

$=$

$\text{'})$

;

expr

$()$

;

$\}$

void var

$()$

$\{$

if

$($

$$lookahead

$=$

$=$

$$ID

$)$

$\{$

match

$($

$$ID

$)$

;

$\}$

else

$\{$

error

$($

$$lookahead$,$ ID

$)$

;

$\}$

$\}$

void expr

$()$

$\{$

var

$()$

;

if

$($

$$lookahead

$=$

$=$

$\text{'}$

$+$

$\text{'})$

$\{$

match

$(\text{'}$

$+$

$\text{'})$

;

expr

$()$

;

$\}$

else if

$($

$$lookahead

$=$

$=$

$\text{'}$

$-$

$\text{'})$

$\{$

match

$(\text{'}$

$-$

$\text{'})$

;

expr

$()$

;

$\}$

$\}$

void prog

$()$

$\{$

begin

$()$

;

stmts

$()$

;

end

$()$

;

$\}$

$//$

$$utility methods

void emit

$($

$$int t

$)$

$\{$

switch

$($

$$t

$)$

$\{$

case

$\text{'}$

$+$

$\text{'}$

: case

$\text{'}$

$-$

$\text{'}$

: case

$\text{'}$

$=$

$\text{'}$

:

cout

$<$

$<$

$$char

$($

$$t

$)$

$<$

$<$

$\text{'}\text{'}$

;

break;

case

$\text{'}$

;

$\text{'}$

:

cout

$<$

$<$

$"$

;

$"$

;

break;

case

$\text{'}$

$\text{'}$

:

cout

$<$

$<$

$"$

$"$

;

break;

case ID:

case KW:

case UID:

cout

$<$

$<$

$$symtab$.$tokstr

$($

$$token$.$tokvalue

$())$

$<$

$<$

$\text{'}\text{'}$

;

break;

default:

cout

$<$

$<$

$"\text{'}$

token

$"$

$<$

$<$

$$t

$<$

$<$

$"$

$,$

$$tokvalue

$"$

$<$

$<$

$$token$.$tokvalue

$()$

$<$

$<$

$"\text{'}"$

;

break;

$\}$

$\}$

void error

$($

$$int t

$,$

$$int expt, const string &str

$)$

$\{$

cerr

$<$

$<$

$"$

unexpected token

$\text{'}"$

;

if

$($

$$lookahead

$=$

$=$

$$DONE

$)$

$\{$

cerr

$<$

$<$

$"$EOF$"$;

$\}$

else

$\{$

cerr

$<$

$<$

$$token$.$tokstr

$()$

;

$\}$

cerr

$<$

$<$

$"\text{'}$

$$of type

$"$

$<$

$<$

$$lookahead;

switch

$($

$$expt

$)$

$\{$

case

$0$

:

$//$

$$default value; nothing to do

break;

case ID:

cout

$<$

$<$

$"$

$$while looking for an ID

$"$

;

break;

case KW:

cout

$<$

$<$

$"$

$$while looking for KW

$\text{'}"$

$<$

$<$

$$str

$<$

$<$

$"\text{'}"$

;

break;

default:

cout

$<$

$<$

$"$

$$while looking for

Step by Step Solution

There are 3 Steps involved in it

1 Expert Approved Answer

Step: 1 Unlock

Question Has Been Solved by an Expert!

Get step-by-step solutions from verified subject matter experts

Step: 2 Unlock

Step: 3 Unlock

Students Have Also Explored These Related Databases Questions!

Q:

Please help fix this code and add anything to it so that it is not limited: #include #include #include #include "token.h " #include "functions.h " using namespace std; ifstream ifs; / / input file...

Q:

Down load parser.zip" from Canvas. This file contains all the material you need. Please modify only the file prog.cpp by adding the methods you need for your parser Please use the following grammar:...

Q:

Please modify only the file prog.cpp by adding the methods you need for your parser. Please use the following grammar: prog - > begin stmt _ list end stmt _ list - > stmt ; stmt _ list | stmt | stmt...

Q:

Do the Following: Down load "parser.zip" from Canvas. This file contains all the material you need. Please modify only the file prog.cpp by adding the methods you need for your parser. Please use the...

Q:

Please help with the code for this problem, please include comments throughout the code. Thanks Obiective: Effectively use loops, lists and/or dictionaries to implement a simple student grade...

Q:

Please help me with code not how to use NetBEAN. Can help make the code work and help me to compile and to RUN Is note how to use NetBean I need help with CODE PLEASE Thank I can Run if the Code work...

Q:

Please please help me with my java homework! Im really despired You are required, but not limited, to turn in the following source files: Assignment6.java (The Assignment6 class extends JApplet)...

Q:

Please help me with my java program, im really depressed you are required, but not limited, to turn in the following source files: Assignment6.java (The Assignment6 class extends JApplet)...

Q:

Please help with how to do this. Thank you During its first month of operation, HFRM completed the following transactions. REQUIREMENT \#6: Prepare an Adjusted Trial Balance in the space below....

Q:

Please help fix my C++ code below, it does not compile. Please fix the necessary so that it would produce the functioning output below. //my code #include #ifndef Course.h #define Course.h class...

Q:

Assuming that the data given below is information in the learning curve for an employee in producing a particular product. Unit # ANAAN28 12 14 16 20 24 30 Time (Hour) 683333539 107 80 64 60 55 51 48...

Q:

Refer to the pizza store location x2 data on pages 522524. What statistical decisions could be made if the 0.01 significance level were selected rather than the 0.05 level?

Q:

Excel issue, my oberservations arent showing correctly I keep putting out 1 0 observations but it keeps only showing 9 , ive tried so many times and nothings working pls help.

Q:

Discutir los principios te ricos detr s del dise o y optimizaci n de reactores catal ticos para procesos qu micos , enfatizando factores como la selecci n del catalizador, la configuraci n del...

Q:

What is the default Aggregation Method in SQL Server Analysis Services in Cube Processing? What are the other options?

Q:

What is the default Aggregation Method in SQL Server Analysis Services in Cube Processing? What are the other standard optional methods?

Q:

Before starting an SQL Server Analysis Services Multidimensional Modeling Project, why is identification of a Data Source important?

Previous Question Next Question