"lvalue required as left operand of assignment" error in C

Applications Programming
1

Hey all. I've been working on some fun with C and decided to write a Rock Paper Scissors game. The problem is, that when I try to compile the file, it gives "lvalue required as left operand of assignment" error. The error line is here:

for ((point1=0 && point2=0); ((point1=3) || (point2=3)); randStart++) {

point1, point2 and randStart are integer values by the way.

I use gcc and vim (which I doubt will help) and can give you all the code, if necessary.

2

Assuming you are wanting to initialise the variables to zero, and loop until one is equal to three:

for( point1 = 0, point2 = 0; point1 == 3 ||  point2 == 3; randStart++) {
1 Like
3

How are point1, point2 and randStart declared?

Also, as agma points out, it looks like you are confusing assignment and comparison:

// '=' assigns x the value 3
x = 3;

// '==' tests if x has the value 3
if (x == 3)
    /* ... */
1 Like
4

A little explanation of an "lvalue" might be in order.

An "lvalue" is something that can have the result of any computation assigned to it - it's pretty much some location in memory where you can put values. The statement "int abc;" declares and integer variable "abc", which can be an lvalue. The address of abc - "&abc" - is not an lvalue, because you can't assign a result to that - the address of the variable is the address. You can assign something to where that address points to by using the "" operator, so "( &abc )" is actually an lvalue. The integer constant "3" is not an lvalue.

The concept of an lvalue is pretty simple once you realize what it means.

5

Thanks all. It seems I was misusing && instead of comma. I also appreciate the info about lvalue. Thank you again.