Ternary operator error

Question

0.00/5 (No votes)

See more:

#include <stdio.h>
int main()
{
int b,i=5;
i==5?b=2:b=4;
printf ("%d",b);
return 0;
}

Syntax error: lvalue required

What I have tried:

The issue gets resolved on using brackets (b=2) & (b=4). I found the answer on internet. But i don't know the reason. Please tell me the reason for it.
Thanks.

Posted 16-Aug-18 2:07am

Member 13922884

Updated 16-Aug-18 2:25am

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2018-08-16T02:26:00

Solution 1

Operator precedence is the problem:

i == 5 ? (b = 2) : (b = 4);

But that is very badly written, and does little of any use.
Instead, try this:

b = i == 5 ? 2 : 4;

which does the same thing by a lot more readably!

Posted 16-Aug-18 2:26am

OriginalGriff

Comments

Member 13922884 16-Aug-18 8:28am

Ok Thankyou !!

OriginalGriff 16-Aug-18 8:34am

You're welcome!

Member 13922884 16-Aug-18 10:05am

b=i==5?2:4; is comprehensible to me. First ternary operator was evaluated and then its value was passed to b.

But how does putting brackets help in the above statement?
Ternary operator have higher precedence than assignment operator,i know. But is b=7 not equal to (b=7).

OriginalGriff 16-Aug-18 10:22am

Because the compiler sees your version as this:

(i==5?b)=(2:b)=4;>/pre>
And goes "Eh? You what? That isn't an LValue!"
The left hand side of <code>a = b </code> must be an LValue - a value that can be assigned to, not a constant, or a result.

Member 13922884 16-Aug-18 12:23pm

Ok. Thanks again.

Member 13922884 16-Aug-18 10:21am

main ()
{
int a=10,b=0,c=7;
If (a?b:c==0)
Printf ("1");
If ((a?b:c)==0)
Printf ("2");
}

In this program brackets are used to evaluate ternary operator before "==" operator. So here i can understand the usage of (). But not in the above program.