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Basic object-oriented programming

30 (33.7%)

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Total Members Voted: 89

[Siquo]

Minor necro, but I have a question on bitshifts. I hope you don't mind.

I'm starting to see a pattern in them. Bitshifting x by y bits is equal to x*2^y, and a bitshift right is x/2^y, right? Or am I completely off my rockers?

Sorry if I'm being ignorant here, as I'm rather new to this stuff.

Yep, and super efficient as well. Although your compiler/pow function might already translate a Pow with a power of two as a bitshift.

[qwertyuiopas]

Probably depends on the optimization level.

[ILikePie]

The Pie is back, and now with even worse code than before, if keep this up, I could be the worst there is. :-P

Anyway, can someone explain why this only works for numbers from 0 to 1023?

Code: [Select]

int int2bin (int input) {
  int output = 0;
  int i = 0;

  while (input - pow(2,i+1) >= 0) i++;
  while (i >= 0) {
    if (input - pow(2,i) >= 0) {
      output = output * 10 + 1;
      input = input - pow(2,i);
      i--;
    } else {
      output = output * 10;
      i--;
    }
  }
  return output;
}


[lordnincompoop]

I'm still confused by enumerated types. Can anyone explain them to me?

[ILikePie]

I'm still confused by enumerated types. Can anyone explain them to me?

If I understand it correctly, it's just a list of stuff where each item in the list has number.
Say you have enum blah {one, two, three}, blah.one + 1 = blah.two, and blah.one = "one". Not so sure about the last part.

[Siquo]

The Pie is back, and now with even worse code than before, if keep this up, I could be the worst there is. :-P

Anyway, can someone explain why this only works for numbers from 0 to 1023?

You reached the end of the universe.

Code: [Select]

  #include <limits>
  std::cout << std::numeric_limits<int>::max()    << std::endl;
And compare that number to the previous number (the output of 1023). Then think of what the next number is going to be.

That number is the max of an int. If you want more, use double, or a string.


Enums are simply names for integers, so you can type
if(checkError() == OVERFLOW_ERROR){ bla }
instead of
if(checkError() == 4){ bla }

They are interchangeable with ints (might need a cast to prevent warnings), but doing actual arithmetic with them is not what they're for. They're to make your code more readable.

[Normandy]

Enumerated types vary from language to language. Neither explanation is correct; generally speaking, an enumerated type is a type that is enumerated. Note the definition of enumerate: http://dictionary.reference.com/browse/enumerate. Thus, an enumerated type is a type that lists all possible values of that type. C++ enums are fairly useless in their current state; C++0x will actually make them less meaningless. In Java or C#, an enumerated type can only take on a certain set of values defined within the class.

[ILikePie]

That number is the max of an int. If you want more, use double, or a string.

Aye, thanks. I wasn't paying attention to the output.

[lordnincompoop]

Oh. Does that mean I can skip that one?

I'm learning C++ by the way.

[eerr]

Oh. Does that mean I can skip that one?

hell no.

Actually I have no idea what you're doing.

[alway]

Oh. Does that mean I can skip that one?

hell no.

Actually I have no idea what you're doing.

Learning enums I would assume. It is a good idea to do it, since various chunks of code you encounter may use them, and for that reason alone it is good to know how they work. As for use, they seem to be mostly for readability rather than adding functionality to your code, since

Code: [Select]

object_state = object_state_running;is much easier to understand than

Code: [Select]

object_state = 2;
Edit after the fact: Turns out I am ending up using them in my current code in order to keep track of the (unchanging) positions of certain important textures within a container. WindowTop is much easier to figure out the meaning of than its value of 6.

[Siquo]

Also: multiple options. If you enum as powers of two, you can use multiple of them as one parameter like this:

initEngine(OPEN_DOOR | START_ENGINE | GO_TO_WORK);

As each encodes a bit and they're added together by the OR operator. The function can then use an AND to check which of the bits were set.

[ILikePie]

God, it's gonna take forever for me to understand those bitwise operators. I understand how they work, more or less, but is there some kind of book/tutorial/guide or whatever you want to call it that explains how you use them?

[Siquo]

http://www.cprogramming.com/tutorial/bitwise_operators.html

Tadaa. It explains how they work, how you can use them, and examples of situations where they can be useful.

[ILikePie]

That's pretty cool, thanks.