What does the operation c=a+++b mean in C/C++?

In C, the expression c = a+++b is parsed by the compiler using the "maximal munch" rule, which means it reads the longest possible token sequence. This expression is interpreted as c = (a++) + b, where a++ is the post-increment operator applied to variable a.

Syntax

c = a++ + b;    // Post-increment a, then add b
c = a + ++b;    // Pre-increment b, then add to a

The key difference lies in operator precedence and associativity. The post-increment operator (++) has higher precedence than the addition operator (+), so a+++b is grouped as (a++) + b.

Example 1: Post-increment (a++ + b)

In this example, a is used in its current value for the addition, then incremented afterward −

#include <stdio.h>

int main() {
    int a = 2, b = 5;
    int c;
    
    printf("Before: a = %d, b = %d\n", a, b);
    c = a++ + b;    // Same as a+++b
    printf("After: a = %d, b = %d, c = %d\n", a, b, c);
    
    return 0;
}

Before: a = 2, b = 5
After: a = 3, b = 5, c = 7

Example 2: Pre-increment (a + ++b)

Here, b is incremented first, then added to a −

#include <stdio.h>

int main() {
    int a = 2, b = 5;
    int c;
    
    printf("Before: a = %d, b = %d\n", a, b);
    c = a + ++b;
    printf("After: a = %d, b = %d, c = %d\n", a, b, c);
    
    return 0;
}

Before: a = 2, b = 5
After: a = 2, b = 6, c = 8

Key Points

• The expression a+++b is always parsed as (a++) + b due to operator precedence
• Post-increment (a++) uses the current value, then increments
• Pre-increment (++b) increments first, then uses the new value
• For clarity, use parentheses to make your intention explicit

Conclusion

The expression c = a+++b in C is interpreted as c = (a++) + b due to operator precedence rules. Understanding increment operators and their timing is crucial for writing predictable C code.