Let us understand all about the error lvalue required as left operand of assignment in C programming language.
We will also showcase an implementation of lvalue and rvalue in C programming. This guide will help you in understanding how to remove lvalue required error in Turbo C, C++, Codeblocks, GCC and other compilers.
The lvalue required as left operand of assignment error occurs irrespective of the programming language because it is the basic syntax of writing an expression.
What is an Expression?
An expression is a valid and well-defined unit of code that resolves to a resultant value which is measurable. This expression can be a mathematical expression that can be evaluated to a value.
This expression can be a combination of constants, numerical values, variables, functions, operators and all these are evaluated to result into an operand.
Any expression is a combination of operators and operands. An operand could be a value, variable, constants, etc.
Must Read: C Programs For Numerical Methods
There are different types of C operators such as:
- Relational operators
- Assignment operators
- Arithmetic operators
- Bitwise operators
- Increment/decrement operators
- Special operators
- Logical operators
Let us see an example of a mathematical expression here.
1 | r = 4x + 3y + z |
A mathematical expression, or any generic expression for that matter, contains two parts viz. lvalue and rvalue.
What is Lvalue?
The lvalue represents the left value in an expression which is the left-hand portion of an expression. So, it is essentially the evaluated result.
If you try to compare it with the above expression example, r is the lvalue which is assigned the result of the right-hand portion.
What is Rvalue?
As you might have guessed it by now, the rvalue represents the right value in an expression which is the right-hand portion of an expression.
This rvalue is the part of the expression that gets computed and assigned to the lvalue of the expression. In this case, it is 4x + 3y + z.
What is lvalue required as left operand of assignment error?
The Left operand of assignment has something to do with the left-hand side of the assignment operator which is the = operator.
Generally, any computation is performed on the right-hand side of the expression and the evaluated result is stored in left-hand side.
1 | c = 3a + 2b |
This error occurs when you try to reverse the way how an expression is evaluated.
1 | 3a + 2b = c |
If you try to perform something like above expression, then it could have two possible meaning:
- The value of c should be stored in 3a + 2b which is not possible and does not make sense either.
- The value of 3a + 2b should be stored in c which goes against the rule of assignment in an expression.
Normally, the assignment operator (equal to operator in this case) assigns the result from right-hand side to left-hand side.
So the above mathematical expression in any programming language will definitely throw the lvalue required error in c programming.
Let us see an example below that generates this error in C programming language.
Note: The following C programming code is compiled with GNU GCC compiler on CodeLite IDE in Windows 10 operating system. However, these codes are compatible with all other operating systems.
Example: Error lvalue required as left operand of assignment GCC Compiler
1 2 3 4 5 6 7 8 9 | #include<stdio.h> int main() { int c, x, y; 2*x + 3*y = c; printf("\nValue of Expression:\t%d", c); return 0; } |
Output
To solve the above error, all you need to do is to reverse the expression. Ensure c should be on LHS and 2*x + 3*y should be on RHS.
The evaluation or the calculation with operators, variables, operands, constants should always be on RHS and it is just the calculated result that should be equated on the right-hand side.
To solve the above lvalue error in C programming, please refer to the following code.
1 2 3 4 5 6 7 8 9 | #include<stdio.h> int main() { int c, x, y; c = 2*x + 3*y; printf("\nValue of Expression:\t%d", c); return 0; } |
One common mistake that programmers often commit is that they tend to use comparison operator == instead of assignment operator =.
Must Read: C Program For Hexadecimal To Binary Conversion
Lvalue Error Examples and Solutions
Error 1: String Comparison
1 | if (strcmp("CodingAlpha", "CodingAlpha") = 0) |
Here, we are trying to compare the strings. However, we have used the = operator which is an assignment and not a comparison operator. Hence, it shall give us the lvalue required error.
Solution
1 | if (strcmp("CodingAlpha", "CodingAlpha") == 0) |
Error 2: Variable Comparison
1 2 3 4 | if (r = 5) { } |
Here you are trying to compare the variable a with a constant value of 5. However, the assignment operator is used instead of the comparison operator and as a result, it will display the error: lvalue required as left operand of assignment.
Solution
1 2 3 4 | if (r == 5) { } |
Let’s discuss more on the error lvalue required as left operand of assignment in the comment section below if you have any compilation errors and any doubts about the same. For more information check Wikipedia.
Thank you so much. I could finally resolve lvalue error in Turbo C software.
I am using Turbo C software for my C programming and I used to get the Lvalue required error in Turbo C very usually. Thanks for this one.
Lvalue Error Examples and Solutions :
2) if(r=5)
{ }.its working correctly .
But if u write as:
if(5=r)
{ }.then it will shown lvalue required error.
and if u write like if(5==r) { }.then it will shown output.