For all you C++ coders out thar

[Vivi Hill]

During one of his first programming labs, a worried student presented his code to the TA, asking "Why is my counter not working?"

Code: Select all

class CountMachine {
   public:
       CountMachine() {
           int counter = 2;           
       } 
       void CountUp() {
           counter++;
       }
};

To which the TA replied, "I'm afraid that's out of the scope of this class."


Also, issues with steam thingie.

[Argent]

Knowing only intro to VB.Net, I can sense a spectacular pun in there, but not knowing C++ I don't think I get it.

[Divide by NaN]

Cute.

[Plasma Waffle]

LOL

[dieinafire]

baddabing!

[rawkies]

ba dum.







tshhhhhhhhhhhhh

[Echoplex]

Could someone make the point of this joke public please

[Vivi Hill]

Could someone make the point of this joke public please

C and C++ have a concept called "scope". If a variable is declared inside curly braces ( { } ), it's deleted as soon as the code reaches the matching right brace. The snippet of code here defines a class, which is a method of storing and manipulating data. In any case, the variable "counter" is declared between the two brackets inside the CountMachine() class constructor (in the "int counter" declaration). Since it's deleted as soon as it hits the "}", it is no longer available outside that constructor. In coding the CountUp() member function, which presumably might be called after construction of a new CountMachine, the programmer is trying to access the "counter" variable declared in the constructor, but, since it's out of scope, the code is invalid.

Thus, the TA is both painting an accurate description of the code and the situation he is in in explaining the reasoning behind the problem in the code. Granted, if learning about scope is out of the scope of the programming course, it's definitely not advanced enough to involve objects.

For the interested, the following would be a correct (if sparse) implementation of the CountMachine class. Since counter is now a member variable, it stays in scope throughout the class and is usable in any functions declared in CountMachine.

Code: Select all

class CountMachine {
   public:
       CountMachine() {
           counter = 2;           
       }
       void CountUp() {
           counter++;
       }
   private:
       int counter;
};

[Echoplex]

I know, that's why I used to term public
Anyway, I've done a couple semesters of Java but I stopped at data structures

[rawkies]

I know, that's why I used to term public
Anyway, I've done a couple semesters of Java but I stopped at data structures

wat.

If you only got to data structures in 2 semesters you had a truly terrible teacher.

[Echoplex]

The Java API does all that stuff for you now so it's not very critical