Thread: Scanning input of different types

  1. #1
    Registered User
    Join Date
    Apr 2012

    Scanning input of different types

    Ok, I am writing a program to read a line of input by the user/from a datafile, and manipulating this data using the ADT stacks. Im having an issue. I have to read in a line of input similar to the following.

    7 3 12 * % 3 13 / + 6 - 17 + p

    Each integer it reads, it has to place it in the stack, but if it reads a operator, then it performs that with the top 2 number on the stack (ex. when it reads * in the line above, it will multiply 12 and 3.

    The problem im having is, how can i make c know if what it is reading is an integer or a character. I tried this with just integers, using scanf and %d as the placeholder. It worked fine, and placed the number in the stack. But as soon as i entered the operators in the line, it gives me a segmentation fault. As of right now, its just scanning everything as a integer, but obviously if there is a + sign, that is not an integer. Any idea how i could read a whole line of data input with integers and characters?

    I wish i could just do:

    if ( input = integer)
        place in stack;     //pseudocode
        if (input = '+');
            perform addition;
        else if (input = '-' );  
            perform subtraction;
    etc, etc. But i dont know how to do this, and i would still be lost on what placeholder to use when scanfing. Any help would be appreciated.


  2. #2
    - - - - - - - - oogabooga's Avatar
    Join Date
    Jan 2008
    You need to read them as strings, with scanf (or fscanf) and %s. Then test the first character to see if it's a digit. If it is, use atoi() to turn it into an integer.
    The cost of software maintenance increases with the square of the programmer's creativity. - Robert D. Bliss

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