C Programming - Expressions - Discussion

Hi @Sumath,

Since C uses left associativity for evaluating expressions to break a tie between two operators having the same precedence.

In given equation, z = x + y * z / 4 % 2 - 1.

* and / has same precedence so 1st divide it into two parts like z= x + y * z and z= z / 4 % 2 - 1. Then, apply the BODMAS rule in these two respectively.

You will get * first then + from the 1st equation.
Then,

/, % and -from 2nd equation.

Then,
Add = sign at the last.

So, finally, you will get;
*/%+-=
as per their precedence.

Hope this helps.

I didn't get it properly, please explain me anyone.

How left associativity is calculated, I didn't understand? Please explain.

Order of evaluation will be compiler specific.
The following program gave me output b = 35..
#include<stdio.h>

int main()
{
int a = 10, b;
b = a++ + ++a + ++a;
printf("b = %d\n",b);
return 0;
}

BUT the GCC also throws a warning as follows:

gcc -Wall -o "scrapbook" "scrapbook.c" -lm (in directory: /home/crownedeagle/Downloads/CDAC C-CAT/C - K&R Solutions)
scrapbook.c: In function \'main\':
scrapbook.c:6:15: warning: operation on \'a\' may be undefined [-Wsequence-point]
b = a++ + ++a + ++a;
^
scrapbook.c:6:15: warning: operation on \'a\' may be undefined [-Wsequence-point]
Compilation finished successfully.

So the compilation of program and evaluation of 'b' will be undefined, it may give different answers on different machines and on different compiler.

My advice: Don't get stuck on this too much.

Hi, I am not getting this, Please anyone explain me.

Please expalin me q=int(a); expression.

int main (void)
{
float a;
int q;

printf("\nInsert number\t");
scanf("%f",&a);

q=(int)a;
++q;

if((q - a) != 1)
printf("\nThe number is not an integer\n\n");
else
printf("\nThe number is an integer\n\n");

return 0;
}

How y=a++differs from y=++a if value of a is 5?

int x=3,y,z;
z=y=x;
z=y+=x=-z;
printf("%d%d%d",x,y,z);

For this code, I get the output as -3 0 0.
But, I can't understand the real execution.
Anyone can explain?

if((i==j||i+j==a+1)&&(i!=1&&i!=a)&&(j!=1&&j!=a)&&(i!=1&&j!=1))

Can anyone plz explain this logic why we use this kind of logic? I cannot understand this.

The above program or logical operation output is 35 because prefix first increment then print and postfix first print then increment. They use one postfix and two prefix.