Please tell me where I messed up

hnkplaya · #1 (**permalink**) 06-28-2007, 09:33 AM

In the Code below i have written for my class i am unsure what I have done wrong. This is suppose to be a calculator for different shapes. This is the instructions from my professor
"If the user enters a character other than t, c, s, or r, tell him that he has to enter one of those four characters, and then have your program exit.

On the other hand, if the user enters a t, you then need to prompt him to enter the base and the height of the triangle. If he enters a c, you need to prompt him to enter the radius of the circle. If he enters an s, you need to prompt him to enter the length of the side of the square. And if he enters an r, you need to prompt him to enter the length and the width of the rectangle."

#include <stdio.h>
#include <math.h>
void main () {
double num, num2, total;
char shape;
char enterkey;

printf ("Please enter a shape:");
scanf ("%c", &shape);

if (shape=='t'){
printf ("\nPlease enter the base of the triangle:");
scanf ("%d", &num);
printf ("\nPlease enter the height of the triangle:");
scanf ("%d", &num2);
total= 0.5 * num * num2;
printf ("area= 0.5 * %d * %d = %d", num, num2, total);

}else if (shape=='c'){
printf ("\nPlease enter the radius of the circle:");
scanf ("%d", &num);
total=2 * 3.14 * num;
printf ("area= 2 * 3.14 * %d = %d", num, total);

}else if (shape=='s'){
printf ("\nPlease enter the side of the square:");
scanf ("%d", &num);
total= 4 * num;
printf ("area= 4 * %d = %d", num, total);

}else if (shape=='r'){
printf ("\nPlease enter the length of the rectangle:");
scanf ("%d", &num);
printf ("\nPlease enter the height of the rectangle:");
scanf ("%d", &num2);
total = num * num2;
printf ("area= %d * %d = %d", num, num2, total);

}else {
printf ("\n I do not know that letter that was inputed please try again!");
}

printf ("\n\n");
scanf ("%c", &enterkey);
}

siLenTz · #2 (**permalink**) 06-28-2007, 10:17 AM

I am C++ programmer, and I think your code is in C right? It is little bit
messy. I think you should use switch() instead of using too many
elseif. Try this

Code:

switch(shape) {
   case 't':

      printf ("\nPlease enter the base of the triangle:");
        scanf ("%f", &num);
       printf ("\nPlease enter the height of the triangle:");
       scanf ("%f", &num2);
       total= 0.5 * num * num2;
       printf ("area= 0.5 * %d * %d = %d", num, num2, total);
      break;

    case 'c':

     // your code....
     break;

    default:
         printf ("\n I do not know that letter that was inputed please try again!");
}

Anyway, is it syntax error or logical error? If it is syntax error pleae
post your errors in here. if it is logical error then tell what happen.

hnkplaya · #3 (**permalink**) 06-28-2007, 10:32 AM

Quote:

Originally Posted by siLenTz

I am C++ programmer, and I think your code is in C right? It is little bit
messy. I think you should use switch() instead of using too many
elseif. Try this

Code:

switch(shape) {
   case 't':
 
      printf ("\nPlease enter the base of the triangle:");
        scanf ("%f", &num);
       printf ("\nPlease enter the height of the triangle:");
       scanf ("%f", &num2);
       total= 0.5 * num * num2;
       printf ("area= 0.5 * %d * %d = %d", num, num2, total);
      break;
 
    case 'c':
 
     // your code....
     break;
 
    default:
         printf ("\n I do not know that letter that was inputed please try again!");
}

Anyway, is it syntax error or logical error? If it is syntax error pleae
post your errors in here. if it is logical error then tell what happen.

It tells me "error C2047: illegal default"

HelloWorld · #4 (**permalink**) 06-28-2007, 12:08 PM

I'm not sure with formatted print using C languages, what do you guys use for double, float, and integers? I just wanted to make sure that your code doesn't have any errors from that. Is there regular println in C languages? What is it? Use it, I think it's much simpler for me than printf....

hnkplaya, can you please post your error for your first code?

rpgfan3233 · #5 (**permalink**) 07-07-2007, 03:49 PM

int printf (char* format, ...);

where format is one of the following:
"%hd" or "%hi" - signed short int
"%hu" - unsigned short int
"%d" or "%i" - signed int
"%u" - unsigned int
"%ld" or "%li" - signed long int
"%lu" - unsigned long int
"%f" - float
"%lf" - double
"%Lf" - long double
"%hx" - unsigned hexadecimal short int (lowercase letters)
"%x" - unsigned hexadecimal int (lowercase)
"%lx" - unsigned hexadecimal long int (lowercase)
"%hX" - unsigned hexadecimal short int (uppercase letters)
"%X" - unsigned hexadecimal int (uppercase)
"%lX" - unsigned hexadecimal long int (uppercase)
"%ho" - signed octal short int
"%o" - signed octal int
"%lo" - signed octal long int
"%c" - single character
"%s" - string of characters (character array, a.k.a. "C(-style) string" or "ASCIIZ string")
"%p" - pointer address
"%n" - nothing printed, but the argument should be a signed int where the number of characters written so far should be stored
"%%" - output a percent (%) sign (since the percent sign is reserved for denoting the position where arguments should be inserted)

I hope that helps. Link for ALL of the specifics of the format string for the printf/scanf family of functions:
printf - C++ Reference

Edit:
Regarding the "illegal default" error, make sure your default case is inside the switch statement and that you closed the switch statement (sometimes you might close the switch statement accidentally or leave it open when it shouldn't be).

HelloWorld · #6 (**permalink**) 07-07-2007, 05:03 PM

is printf new in C++ as it is new in Java? Is there println in C++ as it is in Java

I've read about cout << "Hello" << something like that, but I'm not sure if you can do that as if you do in println() command

that's because I think using println() is much easier than having to remember all % for printf statement, well it's probably better if you can remember all of them, but I think I'd just print what rpgfan said out and put it in front of your computer

or... yeah, go to C++ reference site

rpgfan3233 · #7 (**permalink**) 07-07-2007, 05:14 PM

Quote:

Originally Posted by HelloWorld

is printf new in C++ as it is new in Java? Is there println in C++ as it is in Java

I've read about cout << "Hello" << something like that, but I'm not sure if you can do that as if you do in println() command

that's because I think using println() is much easier than having to remember all % for printf statement, well it's probably better if you can remember all of them, but I think I'd just print what rpgfan said out and put it in front of your computer

or... yeah, go to C++ reference site

printf is not new in C++ because C++ evolved from C. You can think of C++ as an extension of C sort of. In C, you include <stdio.h> to use printf. In C++, you include <cstdio>, which refers to the fact that stdio is a C header. Others in C++ include <cstdlib>, <ctime>, etc. (remove the leading 'c' and add ".h" at the end to convert the header notation to C)

As for Java's System.out.println (or System.Console.WriteLine in C#), there is no such thing in C++. The closest thing to it is the std::endl member:
std::cout << "Hello world!" << std::endl; // C++
// System.out.println("Hello world!"); // Java
// System.Console.WriteLine("Hello world!"); // C#

Of course, if you included "using namespace std;" at the beginning of the C++ program, then you don't need to type "std::" to show that the member belongs to the std namespace.

#8 (**permalink**) 07-27-2007, 08:18 AM

Quote:

Originally Posted by hnkplaya

It tells me "error C2047: illegal default"

what about putting the default on the same line?. i think you should make functions for each case that way it makes the source code a lot easier to read.

HelloWorld · #9 (**permalink**) 07-27-2007, 10:00 AM

Quote:

Originally Posted by andyp guru

what about putting the default on the same line?. i think you should make functions for each case that way it makes the source code a lot easier to read.

For some reason, I don't recommend this... I'd rather have it organized this way:

Code:

case 1:
    // do something
    break;
case 2:
    // do something
    break;

it's much easier to understand and very organized. I don't know if it's only for me, hopefully other programmer feel the same way...?

since programmers write codes so that other programmers can read it!!! XD

rpgfan3233 · #10 (**permalink**) 07-27-2007, 01:27 PM

If you use functions for each case, the only advantage would be in a large switch statement. As long as code is indented enough, there shouldn't be much problem. Of course, if the issue is redundant code, that usually means that you can structure your code better. For example:

Code:

printf("The area of the ");
if (shape == 'r')
    printf("rectangle");
else if (shape == 'c')
    printf("circle");
// etc.
printf(" is %d\n", area);

While it is effective, it isn't exactly ideal. Why not have a variable that holds the name of the shape? Inside the switch statement when figuring out the area of the shape, you could set a string to the value of "rectangle" or "square" or whatever, though the easy way of doing this requires <string.h> (<cstring> in C++, though std::string is better in C++) to be #included:

Code:

char shape_name[10]; //"rectangle" is 9 characters, plus the null terminator makes 10
switch (shape) {
    case 'r':
        strcpy(shape_name, "rectangle");
        // rest of code for rectangle here
    break;

    case 'c':
        strcpy(shape_name, "circle");
        // rest of code for circle here
    break;

    //other cases and default
}
total = num1 * num2;
printf("The area of the %s is %lf\n", shape_name, total);

Just an example of how it might be used. It simplifies the output and doesn't require very much extra code either. That way, there is no need to create your own function and no need to complicate the output.

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