#include "stdafx.h"
#include<iostream>
#include<string>
#include<stdlib.h>
#include<ctype.h>
using namespace std;
class expression
{
private:
char infix[100];
char stack[200];
int top;
int r;
char postfix[100];
public:
void convert();
int input_p(char);
int stack_p(char);
int rank(char);
};
int expression::input_p(char c)
{
if( c== '+' || c=='-' )
return 1;
else if( c=='*' || c=='/' )
return 3;
else if( c=='^')
return 6;
else if( isalpha(c)!=0)
return 7;
else if( c=='(' )
return 9;
else if( c==')' )
return 0;
else
{
cout<<"Invalid expression ::input error\n";
exit(0);
}
}
int expression::stack_p(char c)
{
if(c=='+' || c=='-')
return 2;
else if(c=='*' || c=='/')
return 4;
else if(c=='^' )
return 5;
else if(isalpha(c)!=0)
return 8;
else if(c== '(' )
return 0;
else
{
cout<<"Invalid expression ::stack error\n";
exit(0);
}
}
int expression::rank(char c)
{
if(c=='+' || c=='-')
return -1;
else if(c=='*' || c=='/')
return -1;
else if(c=='^')
return -1;
else if(isalpha(c)!=0)
return 1;
else
{
cout<<"Invalid expression ::in rank\n";
exit(0);
}
}
void expression::convert()
{
cout<<"\n*************************************************\n"
<<"This program converts the given infix expression\n"
<<"in to postfix form"
<<"\n*************************************************\n";
cout<<"Enter an infix expression ::\n";
cin>>infix;
int l=strlen(infix);
infix[l]=')';
infix[l+1]='';
top=1;
stack[top]='(';
r=0;
int x=-1;
int i=0;
char next=infix[i];
while(next!='')
{
while( input_p(next) < stack_p(stack[top]) )
{
if(top<1)
{
cout<<"invalid expression ::stack error\n";
exit(0);
}
postfix[++x]=stack[top];
top–-;
r=r+rank(postfix[x]);
if(r<1)
{
cout<<"Invalid expression ::r<1\n";
exit(0);
}
}
if(input_p( next ) != stack_p( stack[top]))
stack[++top]=next;
else
top–-;
i++;
next=infix[i];
}
postfix[++x]='';
if(r!=1 || top!=0)
{
cout<<"Invalid expression ::error in rank or stack\n";
exit(0);
}
cout<<"\n\nThe corresponding postfix expression is ::\n";
cout<<postfix<<endl;
}
int main()
{
expression obj;
obj.convert();
return 0;
}
1>------ Build started: Project: infix, Configuration: Debug Win32 ------
1>Compiling...
1>infix.cpp
1>z:\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\infix.cpp(94) : error C2137: empty character constant
1>z:\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\infix.cpp(106) : error C2137: empty character constant
1>z:\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\infix.cpp(118) : error C2065: 'top–' : undeclared identifier
1>z:\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\infix.cpp(118) : error C2059: syntax error : ';'
1>z:\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\infix.cpp(132) : error C2065: 'top–' : undeclared identifier
1>z:\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\infix.cpp(132) : error C2059: syntax error : ';'
1>z:\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\infix.cpp(137) : error C2137: empty character constant
1>Build log was saved at "file://\\scidc01\bsprof$\math\arianfar\mydocs\visual studio 2008\projects\infix\infix\Debug\BuildLog.htm"
1>infix - 7 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
it is an infix to postfix program:confused: