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Error Lvalue Required As Left Operand Of Assignment Arduino Board

Originally Posted by C Standard, 6.3.2.1p1

Anlvalue is an expression with an object type or an incomplete type other than void;(53)
if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
When an object is said to have a particular type, the type is specified by the lvalue used to
designate the object. A modifiable lvalue is an lvalue that does not have array type, does
not have an incomplete type, does not have a const-qualified type, and if it is a structure
or union, does not have any member (including, recursively, any member or element of
all contained aggregates or unions) with a const-qualified type.

(footnote 53) The name ‘‘lvalue’’ comes originally from the assignment expression E1 = E2, in which the left
operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
object ‘‘locator value’’. What is sometimes called ‘‘rvalue’’ is in this International Standard described
as the ‘‘value of an expression’’.
An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.

  1. Registered User
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    Oct 2010
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    79

    Lvalue required as increment operand

    #include <stdio.h> int main(void) { int iVar; //line 1 iVar = 20; //line 2 ++iVar; //line 3 printf( "\niVar : %d\n", iVar ); // line 4 iVar--; // line 5 printf( "\niVar : %d\n", iVar ); // line 6 iVar + ++iVar--; //line 7 printf( "\niVar : %d\n", iVar ); // line 8 ++( iVar + iVar ); // line 9 printf( "\niVar : %d\n", iVar ); // line 10 return 0; // line 11 }
    What's the problem?

  2. C++ Witch
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    Look up a C++ Reference and learn How To Ask Questions The Smart Way
    Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    What exactly are you trying to do with these two statements?
    The error message is basically saying that you are trying to increment something that cannot be assigned to, e.g., it is the temporary that resulted from another operation.

  3. Registered User
    Join Date
    Oct 2010
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    This code is pretty much simple arithmetic since my teacher is trying to teach us how to use operators. I don't get why it doesn't add together... Do those statements not work at all?


  4. Registered User
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    Oct 2010
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    79
    That really helps, thanks.


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