Why lvalue is required in shorthand if-else in the else part when using a assignment operator?

Question

    #include <stdio.h>

    void main()
    {
        int k = 8;
        int m = 7;
        int z = k < m ? k = m : m++;
        printf("%d", z);

        k = 8;
        m = 7;
        z = k < m ? m++ : k=m;
        printf("%d", z);
    }

Output

Compile Error:
main.c: In function 'main':
main.c:19:32: error: lvalue required as left operand of assignment
         z = k < m ? m++ : k=m;
                            ^

Why the first assignment works and second doesn't?
And why the compiler tells that lvalue is required?

Stackoverflow was not allowing me post the question, it said my question is mostly code, so i wrote that question — Pankaj Mahato, Jan 25 '14 at 19:10

score 4 · Accepted Answer · edited May 23 '17 at 12:28

4

Due to higher precedence of ?: conditional operator in comparison to =

z = k < m ? m++ : k=m;

Is equivalent to (or say parse as):

z = ((k < m ? m++ : k) = m);
//    ^^^^^^^^^^^^^^^^            
//    expression       = m

m is assigned to an expression that is - Lvalue error.

Read Conditional operator differences between C and C++

edited May 23 '17 at 12:28

Community

1
1

answered Jan 25 '14 at 19:05

Grijesh Chauhan

57,103
20
141
208

Why lvalue is required in shorthand if-else in the else part when using a assignment operator?

1 Answers1