Question

create a c++ code for all possible states for bottom parsing for the following grammar expression:

E

E->E+T

E->T

T->T*F

T->F

F->(E)

F->i

Answer 1

# include <iostream.h>
# include <string.h>
# include <conio.h>

staticchar Stack[50][10]={NULL};
staticint top=-1;
staticint cit=0;

// Input Grammarstaticint productions[6]={5,1,7,7,2,10};

constchar Grammar[5][11][10]={
{"S","E"},
{"E","E+T","E-T","E*T","E/T","E%T","E^T","T"},
{"T","T+F","T-F","T*F","T/F","T%F","T^F","F"},
{"F","(E)","D"},
{"D","0","1","2","3","4","5","6","7","8","9"}
};

// Input Statementconstint input_length=8;
char Input[input_length][5]={"2","*","(","3","+","4",")","$"};

/*************************************************************************///------------------------------ Push( ) ------------------------------///*************************************************************************/void Push(constchar* Token)
{
top++;

strcpy(Stack[top],Token);
}

/*************************************************************************///------------------------------- Pop( ) ------------------------------///*************************************************************************/void Pop( )
{
strset(Stack[top],NULL);

top--;
}

/*************************************************************************///----------------------------- Reduce( ) -----------------------------///*************************************************************************/void Reduce(constint items,constint index)
{
for(int i=0;i<items;i++)
Pop( );

Push(Grammar[index][0]);
}

/*************************************************************************///------------------------------ Shift( ) -----------------------------///*************************************************************************/void Shift( )
{
Push(Input[cit]);

cit++;
}

/*************************************************************************///----------------------- CheckReduceCondition( ) ---------------------///*************************************************************************/constint CheckReduceCondition( )
{
int items;
int index;

char TopItems[100]={NULL};

for(int i=0;i<=top;i++)
{
strset(TopItems,NULL);

for(int j=i;j<=top;j++)
strcat(TopItems,Stack[j]);

for(j=0;j<productions[0];j++)
{
for(int k=1;k<=productions[(j+1)];k++)
{
if(strcmp(TopItems,Grammar[j][k])==0)
{
items=(top-i+1);
index=j;

goto NextCheck;
}
}
}
}

return 0;

NextCheck:

char CitInput[20]={NULL};

strcpy(CitInput,Stack[top]);
strcat(CitInput,Input[cit]);

for(i=0;i<productions[0];i++)
{
for(int j=1;j<=productions[(i+1)];j++)
{
if(strstr(Grammar[i][j],CitInput)!=NULL)
return 0;
}
}

Reduce(items,index);

return 1;
}

/*************************************************************************//*************************************************************************//******************************* main( ) *******************************//*************************************************************************//*************************************************************************/int main( )
{
clrscr( );

int flag=0;

cout<<" /////*****+++++-----..... Bottom-Up Parsing .....-----+++++*****/////";

gotoxy(5,3);
cout<<"Stack";

gotoxy(35,3);
cout<<"Input";

gotoxy(65,3);
cout<<"Next Action";

gotoxy(5,5);

for(int i=0;i<=top;i++)
cout<<Stack[i];

gotoxy(35,5);

for(int j=cit;j<input_length;j++)
cout<<Input[j];

gotoxy(65,5);
cout<<"Shift";

do
{
if(!CheckReduceCondition( ))
{
Shift( );

gotoxy(65,(wherey( )+1));
cout<<"Shift";
}

else
{
gotoxy(65,(wherey( )+1));
cout<<"Reduce";
}

gotoxy(5,wherey( ));

for(int i=0;i<=top;i++)
cout<<Stack[i];

gotoxy(35,wherey( ));

for(int j=cit;j<input_length;j++)
cout<<Input[j];

if(top==0 && strcmp(Stack[top],Grammar[0][0])==0 &&
strcmp(Input[cit],"$")==0)
{
flag=1;

break;
}

elseif(strcmp(Stack[top],"$")==0)
{
flag=0;
break;
}
}
while(1);

if(flag)
cout<<"\n\n Input is Correct...";

else
cout<<"\n\n Input is Incorrect...";

getch( );
return 0;
}