How do I modify a C++ class so that variables that are assigned multiple values only apply the last value assigned?

How do I modify a C++ class so that variables that are assigned multiple values only apply the last value assigned?  Currently, the program accepts an expression and it's assignment variables.
ex. (x+y), x=2, y=3;  Output:  Value = 5  or
(x+2), x=1;   Output: Value = 3

Currently, If I assign multiple values to a variable, it applies the first value assigned.
ex. (x+2), x=2, x=10;   Output: Value = 4

How do I modify the class so that last value assigned is applied?
ex. (x+2), x=2, x=10;   Output: Value = 12

I have attached the main files that are used in the program.  I have tried to make the changes in the SymbolTable class but because of my limited expereince with programming and C++ I couldn't get it to compile.
main.cpp
symboltable.cpp
variable.cpp
NSing9Asked:
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Infinity08Connect With a Mentor Commented:
I would make your SymbolTable::insert function a bit more intelligent. ie. check whether the variable name is already in the symbol table, and if so, just change the value. If the variable name is not yet in the symbol table, you can insert a new entry.
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mifergieCommented:
Looks to me like you have a stack that you are pushing assignments onto.  When you pop them off you first pop off the last item and x gets assigned properly, then you pop the first item off and assign x improperly.  To fix it, change this operation so that it acts as a FIFO - or a ring buffer.
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NSing9Author Commented:
That's the problem.  I don't know quite how to do that.
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NSing9Author Commented:
I've tried adding a second insert method that supplies only the variable name.  I was trying to have this method called when the variable name is encountered and have the original insert method check whether the variable is already in the symbol table.  I'm not having any luck with getting this approach to compile.  Any suggestions on coding with your approach?
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Infinity08Commented:
Could you show the code you tried (that didn't compile) ?
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