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# Error: Expression must be a modifiable lvalue

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### #1Stickmunkee  Members   -  Reputation: 108

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Posted 17 January 2013 - 03:29 PM

I've looked around gamedev some and it seems like there's a really supportive community, so I decided to try getting support on this error I'm getting.

I'm learning C++ from a book; I'm just beginning in it, so this is a really simple program. The idea is: the user enters a number, which the computer guesses at. However, in the section where I'm modifying the ai's guessing logic, I'm getting an error I can't find a good way to get around. I included a picture of the code and error. When I hover my mouse over the variables "guess" in the arithmetic within the 'if' blocks, it says: "Error: Expression must be a modifiable lvalue"

I would really appreciate an explanation of what that means and maybe a suggestion to fix it.

Many thanks in advance for helpful replies.

### #2fastcall22  Crossbones+   -  Reputation: 3637

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Posted 17 January 2013 - 03:46 PM

Quickfix:
Use a=4+b over 4+b=a.
You cannot assign the value a into 4+b.

If both a=4+b and 4+b=a are to be the same, then which value should be assigned to the other in the expression: a=b?
You can read more about l-values and r-values here.

Also:
You only need to call srand once in your program, please refer to this thread: Why is it bad to call srand multiple times?

Edited by fastcall22, 17 January 2013 - 03:54 PM.

WW91J3ZlIGdvdCBhIHNlY3JldCBib251cyBwb2ludCE=

### #3Stickmunkee  Members   -  Reputation: 108

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Posted 17 January 2013 - 03:58 PM

Thank you, this is very helpful

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