Error expected primary-expression before 'if'

Question

I am just a student and beginning to learn C programming, so I am not really on an advanced level.

I have this piece of code, and I guess that it is pretty easy to understand what I am trying to do. However I get an error saying an error before if.

I suspect that the problem is my if-else statement in between the if and else. How would you guys solve it?

#include <stdio.h>
#include <iostream>
int main ()
{
int N;
scanf("%i",&N);
if (N > 50)
        (if (N > 75)
            N = N - 25;
            N = N - 10;
        )
else
        N = N + 10;
printf("%i",N);
}

use %d instead of %i and also set parenthesis{} of if. e.g if(){ } else{} — Salman, Oct 23 '17 at 18:06
1) Consider learning from a [good C++ book](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list), not by trying to code randomly. 2) When asking about compilation errors - copy/paste the error. 3) Voted to close as typo due to obvious reasons. — Algirdas Preidžius, Oct 23 '17 at 18:06
`(if (N > 75) N = N - 25; N = N - 10; )` --> `{ if (N > 75){ N = N - 25; N = N - 10; } }` or `{ if (N > 75) N = N - 25; N = N - 10; }` ? — BLUEPIXY, Oct 23 '17 at 18:07
Why do you use the C++ tag when learning C? Why do you use `#include ` when learning C? Or are you learning C++? Then why do you use printf instead of cout? — , Oct 23 '17 at 18:08
Trying to coalesce @manni66 's point, it looks like you are simultaneously learning C and C++. Be warned these are two different languages. C++ can often compile C code, but not always and there are no guarantees this will result in an optimal solution. C can rarely compile C++ code, and when it can, the C++ code that can compile eschews all that is C++. — user4581301, Oct 23 '17 at 18:20

Vlad from Moscow · Accepted Answer · 2017-10-23T18:26:02.557

Taking into account the error message it seems that you are compiling the program as a C++ program. Otherwise the compiler at first would issue a message about the wrong header <iostream>.

If it is a C++ program then there is no need to use functions from the header <stdio.h> that moreover in C++ should be included like

#include <cstdio>

So I advice to remove the header and to use the standard C++ native I/O functions.

Also instead of braces you enclosed in parentheses the substatement of the if statement.

if (N > 50)
        (if (N > 75)
            N = N - 25;
            N = N - 10;
        )

And it is obvious if N is greater than 75 then it is evident it is greater than 50. So the first if statement also may be removed.

And it is a bad idea to use a capital letter for naming an ordinary variable.

Taking all this into account the program can look like

#include <iostream>

int main()
{
    int n;

    std::cin >> n;

    if ( n > 75 )
    {
            n = n - 25; // or n -= 25;
            n = n - 10; // or n -= 10;
    }
    else
    {
        n = n + 10; // or n += 10;
    }

    std::cout << n << std::endl;
}

If you want to use standard C I/O functions then the program can look like

#include <cstdio>

int main()
{
    int n;

    std::scanf( "%i", &n );

    if ( n > 75 )
    {
            n = n - 25; // or n -= 25;
            n = n - 10; // or n -= 10;
    }
    else
    {
        n = n + 10; // or n += 10;
    }

    std::printf( "%i\n", n );
}

If it is a C program and the header <iostream> is included by mistake then the program can look like

#include <stdio.h>

int main( void )
{
    int n;

    scanf( "%i", &n );

    if ( n > 75 )
    {
            n = n - 25; // or n -= 25;
            n = n - 10; // or n -= 10;
    }
    else
    {
        n = n + 10; // or n += 10;
    }

    printf( "%i\n", n );
}

@NaseefUrRahman The format specifiers "%I" and "%d" are interchangeable. — Vlad from Moscow, Oct 25 '17 at 18:56

Naseef Chowdhury · Answer 2 · 2017-10-25T15:54:29.887

0

Just change the ( with { after if condition. I have edited your code -

#include <stdio.h>
#include <iostream>
int main ()
{
int N;
scanf("%d",&N);
if (N > 50)
        {
            if (N > 75)
            N = N - 25;
            N = N - 10;
        }
else
        N = N + 10;
printf("%d",N);
}

edited Oct 25 '17 at 15:54

answered Oct 23 '17 at 18:09

Naseef Chowdhury

2,357
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You shouldn't use `%i` for `scanf`. See [here](https://stackoverflow.com/questions/17329647/i-or-d-to-print-integer-in-c-using-printf). Instead, use `%d`. – Nik Oct 23 '17 at 18:19

Error expected primary-expression before 'if'

2 Answers2