Lvalue required error in C

Question

my code is:

#include<stdio.h>
int main() {
   int a=10, b;
   a >= 5 ? b=100 : b=200;
   printf("%d %d", a, b);
   return 0;
}

Here comes a "Lvalue Required" in the line of conditional operator.

Can you explain me why?

By the way, the same program is perfectly working in C++.

yes. it is working out with parentheses... but the older one is still working in C++. i just wanted to know the reason that why there is an error in C then? — Himanshu Aggarwal, Mar 03 '13 at 19:58
@Tim :) :) This is not good reason, You may like [Charles Bailey's answer](http://stackoverflow.com/questions/1082655/conditional-operator-differences-between-c-and-c/1082680#1082680) for technical reason. — Grijesh Chauhan, Mar 03 '13 at 20:28

score 7 · Accepted Answer · edited May 23 '17 at 12:12

7

The idiomatic way to write that assignment is:

b = (a >= 5) ? 100 : 200;

If you insist on keeping it your way, add parentheses:

(a >= 5) ? (b=100) : (b=200);

For details on why this works in C++ but not in C, see Conditional operator differences between C and C++ (thanks @Grijesh Chauhan!)

edited May 23 '17 at 12:12

Community

answered Mar 03 '13 at 19:54

NPE

yes. it is working out with parentheses... but the older one is still working in C++. so why there is an error in C then? – Himanshu Aggarwal Mar 03 '13 at 19:57
1

@HimanshuAggarwal [**Conditional operator differences between C and C++**](http://stackoverflow.com/questions/1082655/conditional-operator-differences-between-c-and-c) – Grijesh Chauhan Mar 03 '13 at 20:03

score 1 · Answer 2 · answered Mar 03 '13 at 21:54

1

parenthesis have the higher precedence in C.. U get the warning due to precedence problem.. Try this..

(a >= 5) ? (b = 100) : (b = 200);

answered Mar 03 '13 at 21:54

2 Answers2