problem in using ungetch( )

[cworld]

Hi all
I am making an RPN calculator in which i want to read data from input. so i used getchar( ) and able to read character by character. But when the while condition fullfill then it comes out from the loop but retain the next character read from input so i want to ungetch to the input. but it does not work. Plz help me, my code is:

/******** Program for Read_Input Function**********/
 
# include <stdio.h>
# include <ctype.h>
# include <conio.h>
# include "rpn.h"
char in[10];
char c;
 
read_input(char in[10])
 
    {
 
    int i;
        c=getchar();
            in[0]=c;
            in[1]='\0';
 
        if (c==' '||c=='\t')
 
        while ((c=getchar())==' '||c=='\t');
 
        if(isdigit(c))
        {
        i=1;
 
        while (isdigit(c=getchar()))
            in[i++]=c;
            in[i]='\0';
        if (c!=EOF)
            printf("Value of c before Ungetch= %d\n",c);
            ungetch(c);
 
        return NUMBER;
            }
 
        if(isalpha(c))
 
            return ERROR_ALPHA;
return c;
    }
/****************************************/

This function is called in the main program but again when i call this function it gets the next charater from the input. should i make a userdifine function for getch and ungetch like as given in Ritchie book chapter4. or some otherthings??

thankyou
cworld

[JosAH]

Hi all
I am making an RPN calculator in which i want to read data from input. so i used getchar( ) and able to read character by character. But when the while condition fullfill then it comes out from the loop but retain the next character read from input so i want to ungetch to the input. but it does not work.

The ungetch() function is part of the conio stuff which doesn't use the streams
used by the stdio library. You should use the ungetc() function instead; it will
put back the last character read in the input stream.

kind regards,

Jos

[cworld]

The ungetch() function is part of the conio stuff which doesn't use the streams
used by the stdio library. You should use the ungetc() function instead; it will
put back the last character read in the input stream.

kind regards,

Jos

Thankyou Jo for your quick response.
but still i m getting error:
************************************************** *
error C2660: 'ungetc' : function does not take 1 parameters stack.cpp
************************************************** *
Actually i am taking input from keyboard so it should return character to the keyboard, but it does not work.

any idea?

cworld

[JosAH]

but still i m getting error:
************************************************** *
error C2660: 'ungetc' : function does not take 1 parameters stack.cpp
************************************************** *
Actually i am taking input from keyboard so it should return character to the keyboard, but it does not work.

any idea?

Yep, I have an idea: the ungetc() function takes one parameter which is the
character to put back in the stream, exactly as your compiler's diagnostic
message tried to tell you.

kind regards,

Jos