A strange error

Here is the main.cpp from my program .Everything works fine when the while loop is not there...i.e..it is done only once..

Code:

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#include <iostream>
#include <string>
#include "token.h"
#include "rpn.h"
#include "shunt_y.h"
using namespace std;

int main()
{

    deque<token> dt;
    char q;
    string input;
   
    while(1)
    {
    cout<<"Enter the expression:\n>";
    getline(cin,input);
    dt = tokenize(input);
    dt = infix_to_rpn(dt);
    cout<<rpn_eval(dt)<<endl<<"Quit?\n>";
    cin>>q;
    if (q == 'y' )break;
    else continue;
    }
    return 0;

}

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At runtime....whenever I opt not to quit....the input string automatically assumes a garbage value...not letting me into type into the prompt...
Looks somewhat like the following quote:

Quote:

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Enter the expression:
>log ( 10 ^ 5 ) - sin ( 3.142 / 2 )
4
Quit?
>n
Enter the expression:
>0
Quit?
>n
Enter the expression:
>0
Quit?
>

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and so on...

__fixed it__on a suggestion that I should have put a

Code:

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cin.ignore(numeric_limits<streamsize>::max(),'\n');

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after the

Code:

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cin>>q;

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Correct, the cin >> q leaves the newline in the buffer. cin.ignore clears the input buffer.
Also, else continue; is unnecessary. The loop while repeat once it reaches the end anyway.
Also consider indenting better.

Your console input buffer is not fully empty that's why you are not allowed to use that...
Use instead. Try reading ignore function provided by cin...

And by the way that's not a strange error... :-)

Quote:

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Your console input buffer is not fully empty that's why you are not allowed to use that...

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Not quite true. You are allowed to use it alright.

The thing is that there is an unread newline character. getline reads anything up to the first newline character. If there are no other characters preceeding the newline, it means that getline successfully extracted an empty line (empty string).

you also could have initialised your input string to " " at the start of the loop
i think.....

Quote:

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Not quite true. You are allowed to use it alright.

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My bad..... I didn't mean to write that...
I know we still can use that but what i mean was to write console ignore to clear your buffer out... Anyways, nice compilation of my statement :-)

Quote:

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Originally Posted by bobknows

you also could have initialised your input string to " " at the start of the loop
i think.....

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What good would that do?