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Dior Anderson
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Asked: 2022-05-18T20:58:42+00:00 In:

Solving the error: c++ expression must be a modifiable lvalue

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I’m building a new program, but when I run it, an error pops up. The error displayed is as follows:

Error: expression must be a modifiable value

I have tried several workarounds, but they still do not get the desired results. If you have come across this situation and have a solution for the “c++ expression must be a modifiable lvalue” problem, pls let me know. Here is what I do:

int M = 3; 
 int C = 5; 
 int match = 3;
 for ( int k =0; k < C; k ++ )
 {
  match --; 
  if ( match == 0 && k = M )
  {
  std::cout << " equals" << std::endl;
  }
 }
if ( match == 0 )

Thanks!

c++ expression must be a modifiable lvalue
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2 Answers

  1. Best Answer
    Expert

    The cause: Because a cast does not yield an lvalue – a value that can be utilized on the left side of an assignment. This error message is displayed.

    Solution:

    Because && has higher precedence than the assignment operator, your condition is similar to:

    if ((match == 0 && k) = m)

    You cannot assign it to the left-hand side of this because it is a rvalue, namely the boolean returned by the evaluation of the subexpression match == 0 && k.

    In contrast, comparison takes precedence, therefore the equivalent of match == 0 && k == m is:

    if ((match == 0) && (k == m))
    • 0

  2. If you declare a in C, you’ll also get the same error. 

    char array[size];

    Then, assign a value to the index position without specifying an index position. 

    array = '\0';

    Doing: 

    array[index] = '0';

    You’re specifying the accessible/modifiable address previously declared.

    • 10

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