Use character variable as operator

I'm trying to use a user-inputted character variable as an operator, similar to the following:

Code:

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int num1 = 5;
int num2 = 5;
int sum;
char oper;

cin >> oper;

sum = (num1 oper num2);

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I'm new to programming, and wasn't sure if this is possible. I know how to do it in a different way with a switch statement on the oper variable, but would like to know if it's possible to convert the oper variable in some way that it would be possible to utilize "sum = (num1 oper num2);" without a compilation error. Anyone know?

in some languages (python and lisp that I know of), this is possible, but not in C++.
you could use a switch statement to get around this.

I don't think you can do that. C++ is not an interpreted language. It doesn't have interpreters. Only way I know of (using only C++) is to build your own eval type-of thing. Which will invariably use a switch statement.

But maybe someone knows better.

Invariably. You will use a switch statement to do this operation! :)

It doesn't absolutely have to be a switch statement but it is probably the easiest:

Code:

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switch(oper)
{
case '*' :
    sum = num1 * num2;
    break;
etc... etc... etc...
}

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And what happens if I enter "q"? ;)

then big people with black suits and dark cars will knock on your door. OR you will use default.

Quote:

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Originally Posted by jafet

And what happens if I enter "q"? ;)

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Code:

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cout << "What part of don't enter 'q' do you not understand?";

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:)

You could store function pointers in a std::map, using characters as keys. While this wouldn't validate the num1 oper num2 syntax (Which is impossible, anyway), you could use myFunctionMap[oper](num1, num2).

try this:

http://cboard.cprogramming.com/showt...ht=string+sums

Quote:

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Originally Posted by DrkMatter

You could store function pointers in a std::map, using characters as keys. While this wouldn't validate the num1 oper num2 syntax (Which is impossible, anyway), you could use myFunctionMap[oper](num1, num2).

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Bad idea. At the very least you must first look up the pointer and test if it actually evaluates to something.