Help with simple function

This is a discussion on Help with simple function within the C Programming forums, part of the General Programming Boards category; Hi guys, first post so take it easy. I just started programming yesterday in C. And decided to try and ...

  1. #1
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    Help with simple function

    Hi guys, first post so take it easy. I just started programming yesterday in C. And decided to try and write a simple programme to calculate the cos of a user input value. This is my attempt so far but its not working
    Code:
    #include <stdio.h>
    #include <math.h>
    main()
    {
    int d;
    float x;
    	printf("welcome to the cos calculator\n");
    	printf("what angle do you want the cos of:\n");
    	scanf("%d" &d);
    	x=cos(d);
    	printf("x=%0.2f\n",x);
    }
    I know this is probably completely wrong so any help would be much appreciated
    Thanks

  2. #2
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    Code:
    	scanf("%d", &d);
    Btw, Read the documentation of all functions you used.google is your friend.

    The cos() function returns the cosine of x, where x is given in radians.

  3. #3
    Epy
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    The main function needs a type specifier, namely int:

    Code:
    int main()
    {
        ...
        return 0;
    }
    Need a comma in that scanf statement:

    Code:
    scanf("%d", &d);
    Pretty sure the cos function expects radians, so you'll need to convert from degrees to radians.

  4. #4
    Registered User ssharish2005's Avatar
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    There is some syntax error in the code and logic is quite right. Few things which picked

    Code:
    main() should be int main()
    Main should always return int. Perhaps with the C99 if you ignore it is interpreted as int.

    Code:
    scanf("%d", &d);
    Missed the comma between the format specifier and the argument list. And also note you might have to clear the input buffer, to avoid any buffer issues when reading value furthre on.

    Code:
    return 0;
    Missed the return value. Main must return.

    ssharish
    Life is like riding a bicycle. To keep your balance you must keep moving - Einstein

  5. #5
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    cos() expects a double. Conversion is implied but your compiler should have given you a warning when you passed it an int. It returns a double, so when you assign to a float there's another conversion implied. In the end it's probably easiest to only work with doubles.

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    Thanks guys, I got it to work with the following code, I then added a bit more on to see how much i could do. But i have 2 questions. Firstly why do you have to put "int" in front of "main ()" as we did not have to that for other stuff we learned in class.
    Code:
    #include <stdio.h>
    #include <math.h>
    int main()
    {
    int r;
    double x;
    double d;
    	printf("welcome to the cos calculator\n");
    	printf("what angle do you want the cos of):\n");
    	scanf("%d", &r);
    	d=r*0.01745;
    	x=cos(d);
    	printf("x=%0.5f\n",x);
    int y;
    printf("are you happy with the answer?(yes=1/no=0)\n");
    scanf("%d",&y);
    	if(y==1) {
    	printf("huzzah!!\n");
    	}
    	else if(y==0){
    	printf("Too bad, it's right!\n");
    	}
    }
    and second of all, I had to use integers for the yes/no part at the end, because I couldn't figure out how to just use the input "y" or "n". How could I've done this instead?
    Many thanks, alex

  7. #7
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    int main() vs. void main()

    To read a single char, you can use getchar()

  8. #8
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    Thanks guys, I got it to work with the following code, I then added a bit more on to see how much i could do. But i have 2 questions. Firstly why do you have to put "int" in front of "main ()" as we did not have to that for other stuff we learned in class.
    Code:
    #include <stdio.h>
    #include <math.h>
    int main()
    {
    int r;
    double x;
    double d;
    	printf("welcome to the cos calculator\n");
    	printf("what angle do you want the cos of(in radians please):\n");
    	scanf("%d", &r);
    	d=r*0.01745;
    	x=cos(d);
    	printf("x=%0.5f\n",x);
    int y;
    printf("are you happy with the answer?(yes=1/no=0)\n");
    scanf("%d",&y);
    	if(y==1) {
    	printf("huzzah!!\n");
    	}
    	else if(y==0){
    	printf("Too bad, it's right!\n");
    	}
    }
    and second of all, I had to use integers for the yes/no part at the end, because I couldn't figure out how to just use the input "y" or "n". How could I've done this instead?
    Many thanks, alex

  9. #9
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    Quote Originally Posted by alexl View Post
    Firstly why do you have to put "int" in front of "main ()" as we did not have to that for other stuff we learned in class.
    Fire your teacher! Then, check out the link Bayint Naung provided, or check here. It's always best to be explicit and follow the standard, since you never know what compiler somebody else may be using.
    and second of all, I had to use integers for the yes/no part at the end, because I couldn't figure out how to just use the input "y" or "n". How could I've done this instead?
    Many thanks, alex
    Code:
    printf("are you happy with the answer?(yes=y/no=n)\n");
    scanf("%c", &c);
    if (c == 'y') {
        printf("huzzah!!\n");
    }
    else if(y == 'n') {
        printf("Too bad, it's right!\n");
    }
    else {
        printf("Can't you follow directions?  I said press 'y' or 'n'!\n");
    }

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