C issue with first calculation program

Question

I am transfering from Java to C and C++ and i am having a problem with easiest tasks like this so please help me if you can:

#include<stdio.h>
#include<math.h>

 void main()
 {
int a, h;
double interres;
double base;
printf("Input  a: ");
scanf("%d", &a);
printf("Input  height h: ");
scanf("%d", &h);
base =(a^2 * sqrt(3))/ 4;//line 13
interres = a ^ 2 * sqrt(3);//line 14

printf("(%d^2*sqrt(3))/4=(%d^2*%f)/4=(%f*%f)/4=%f/4=%f cm",a,a,sqrt(3),a^2,sqrt(3),interres,base);

 }

And I get constantly errors:

error C2297: '^': illegal, right operand has type 'double' line 13
error C2297: '^': illegal, right operand has type 'double' line 14
 warning C4996: 'scanf': This function or variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS.  warning C4996: 'scanf': This function or variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.

See the answer to this question for the problem with `^`: http://stackoverflow.com/questions/4843304/why-is-my-power-operator-not-working and for the problem with scanf, try changing it to `scanf_s` as suggested. — nonzaprej, May 03 '17 at 10:57
`^` is the _exclusive-OR_ operator. There is no exponentiation operator in C. — Ian Abbott, May 03 '17 at 10:57
i wanted to make an exponentiary operator.is there any other solution — Mapet, May 03 '17 at 10:59
If there was a way to see what the `^` operator is for ... There really should be something to search the internet for such things. Or maybe a book explaining the C language. — too honest for this site, May 03 '17 at 11:28
Wht did you learn about exponentation at school? Maybe there is a way to rewrite `a ** 2` to `a * a`? (`**` is **not** a C operator!) — too honest for this site, May 03 '17 at 11:32
@Ian - `pow()` is a poor choice for integer powers, and a very poor choice for squaring integers (it is slower, and introduces much more error). — Toby Speight, May 03 '17 at 14:53

score 0 · Answer 1 · answered May 03 '17 at 15:04

Several issues:

In C and C++, main returns int, not void. Unless your compiler documentation explicitly lists void main() as a valid signature, using it invokes undefined behavior. main should be defined as

int main( void )

if you don't take any command line arguments, or

int main( int argc, char **argv )

if you do.

Secondly, the ^ operator is the bitwise XOR operator, not an exponentiation operator; neither C nor C++ have an exponentiation operator. You must either use the pow function in the standard library or roll your own.

Finally, scanf can be unsafe when reading input with either the %s or %[ conversion specifiers, which you aren't doing. Personally, I'd disable the warning as described in the error message.

score -1 · Answer 2 · answered May 03 '17 at 11:13

-1

#include<stdio.h>
#include<math.h>

 void main()
 {
int a, h;
double interres;
double base;
printf("Input  a: ");
scanf("%d", &a);
printf("Input  height h: ");
scanf("%d", &h);
base =(double)((a*a) * sqrt(3))/ 4;//line 13
interres =(double) (a *a)  * sqrt(3);//line 14

printf("(%d^2*sqrt(3))/4=(%d^2*%f)/4=(%f*%f)/4=%f/4=%f cm",a,a,sqrt(3),a*a,sqrt(3),interres,base);

 }

answered May 03 '17 at 11:13

Ahmed Nabil El-Gawahergy

26
3

Indentation............... – ThingyWotsit May 03 '17 at 11:44

C issue with first calculation program

2 Answers2