Thread: Arguments and type casting

  1. #1
    Registered User
    Join Date
    May 2006

    Arguments and type casting

    I wanted to start learning C, and I just got to arguments and they are pretty useful and I decided to write a celsius to fahtrenheit program that took the celsius degree as an arg and typecast it to type long so I could do the calculation. I don't know what's wrong, but I always get a really big negative number. Here is the code:

    1:      /**************************************
    2:       * cels2fahr.c:
    3:       * A program that takes an integer as an argument
    4:       * and converts it from Celsius (C) to Fahrenheit
    5:       * (F).
    6:       ************************************/
    8:      #include <stdio.h>
    10:     int main(int argc, char *argv[]) {
    12:             int fahr = 0;
    14:             if (argc < 2) {
    15:                     printf("Proper Usage: \n");
    16:                     printf("cels2fahr <DEGREES IN CELSIUS>\n\n");
    17:                     return 1;
    18:             }
    20:             fahr = (9.0/5.0) * (long) argv[1] + 32;
    22:             printf("%d\n", fahr);
    24:             return 0;
    25:     }

  2. #2
    Registered User
    Join Date
    Jan 2005
    Arguments are charactor arrays, you can't just type cast them and have them changed to a numeric representation for you. There is the atoi function that accepts a char pointer and returns it's numeric value.

  3. #3
    Frequently Quite Prolix dwks's Avatar
    Join Date
    Apr 2005
    Did you actually try to compile the code with the line numbers in? That won't work.

    atoi() . . . sscanf() is better. See the FAQ.

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  4. #4
    Registered User
    Join Date
    May 2006
    No, I wrote a program that lists it out like that for me and I copied/pasted it onto here. Ok, so I need to use atoi()? I will get right on that.

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