Jump to content

  • Log In with Google      Sign In   
  • Create Account

- - - - -

Power Operator


Old topic!
Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.

  • You cannot reply to this topic
14 replies to this topic

#1 Jason Goepel   Members   -  Reputation: 442

Like
0Likes
Like

Posted 16 December 2013 - 02:25 PM

Many of my users write math-oriented scripts.  Do you have any opposition to a binary operator that computes power?

 

I was thinking that ** wouldn't cause any conflicts since AngelScript doesn't support * for pointer dereferencing.



Sponsor:

#2 Andreas Jonsson   Moderators   -  Reputation: 3444

Like
0Likes
Like

Posted 16 December 2013 - 07:02 PM

I think that might work, yes.

Are you planning to implement this support?
AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

#3 Jason Goepel   Members   -  Reputation: 442

Like
0Likes
Like

Posted 17 December 2013 - 07:57 AM

I was going to either implement it in the compiler or as a pre-processing feature, depending on whether you would accept it in the compiler (I didn't want to maintain a fork).

 

The C-runtime "pow" function always returns a floating-point number.  Do we want this behavior even if the operator is used between two integers (i.e.  3 ** 4 ==> 81.0 )?



#4 _Vicious_   Members   -  Reputation: 240

Like
0Likes
Like

Posted 17 December 2013 - 09:14 AM

Something like this might also be used for vector cross products.



#5 Jason Goepel   Members   -  Reputation: 442

Like
0Likes
Like

Posted 17 December 2013 - 09:46 AM

Of course, this operator would be able to be overloaded like any of the other math operators.

 

Regarding my earlier post, I am inclined to make ** not always return a double.  I am inclined to think it should behave like the other math operators and return the same type as the operands when possible.  I will look into an integer implementation that is better than a simple multiply loop.



#6 Andreas Jonsson   Moderators   -  Reputation: 3444

Like
0Likes
Like

Posted 17 December 2013 - 04:56 PM

If the power-of operator is implemented as a built-in operator it should keep the type of the operands (with appropriate implicit casts when they are not equal). Much like how it is done for other math operators.

 

And yes, it should be possible to overload it as well for, e.g. by registering/implementing the opPow/opPow_r methods.

 

You'll need to implement new bytecode instructions for this too. Internally in the bytecode instructions can possibly use the pow() function and then convert the result to the correct type. This is of course if you don't find a more efficient way of calculating power-of. :)


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

#7 Jason Goepel   Members   -  Reputation: 442

Like
0Likes
Like

Posted 18 December 2013 - 09:48 AM

I think I will implement my own integer power function.  I've done some limited testing and found that it is up to ten times faster to do the calculation with integers than to pass integers through the floating-point pow() function.

 

Where should I put the powi and powi64 functions?  Should I create a new file in the project?

 

Also, it is fairly easy for powi to overflow.  Should I detect overflows and set an exception?  Overflow detection is pretty cheap.  I can pre-calculate a table with 64 entries and assign the maximum value of a base for any given exponent.  For my users I think it would be helpful to see an overflow exception.



#8 Andreas Jonsson   Moderators   -  Reputation: 3444

Like
0Likes
Like

Posted 18 December 2013 - 11:35 AM

You can just add the powi and powi64 functions to one of the existing modules, e.g. as_context.cpp where I assume they will be most frequently called. Once I merge the code into the SVN I'll consider creating separate file for these utility functions or not.

 

Try to keep the way the operators work the same regardless on the type they're working on. I agree that having an overflow exception can be useful (similar to the division by zero exception), but the float and double versions should also throw the same exception.


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

#9 Jason Goepel   Members   -  Reputation: 442

Like
0Likes
Like

Posted 19 December 2013 - 04:44 PM

Here's my attempt at a ** and **= operator.  I've tested it with VS 2013 and MinGW GCC 4.8.1.

 

Let me know if you have any questions.

Attached Files



#10 Andreas Jonsson   Moderators   -  Reputation: 3444

Like
0Likes
Like

Posted 19 December 2013 - 06:12 PM

Thanks a lot. I'll review the patch and merge it into the trunk as soon as I can.


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

#11 Jason Goepel   Members   -  Reputation: 442

Like
0Likes
Like

Posted 20 December 2013 - 07:07 AM

I've done some more thinking about the overflow exceptions.  The C-runtime implementations vary on whether or not they set errno to ERANGE.  They do all seem to return HUGE_VAL though.  Perhaps the integer implementation should not overflow, but instead return INT_MAX.

 

There are also inconsistent implementations of 0**0.  Microsoft seems to return 1.



#12 Andreas Jonsson   Moderators   -  Reputation: 3444

Like
0Likes
Like

Posted 20 December 2013 - 03:11 PM

The most important part is to be consistent. Perhaps you're right not to raise an exception in this case and instead return INT_MAX, but then the float and double variants my behave consistently and return the largest possible value.


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

#13 Andreas Jonsson   Moderators   -  Reputation: 3444

Like
0Likes
Like

Posted 20 December 2013 - 07:25 PM

I took a quick look at the patch. It looks like everything is OK. You even took the time to update the documentation. Nice!

 

I'll be doing a bit of testing before I check in the changes, but rest assured that this will be part of the 2.28.1 release. :)


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

#14 Jason Goepel   Members   -  Reputation: 442

Like
0Likes
Like

Posted 21 December 2013 - 07:23 AM

I would have felt bad if I only did the fun part smile.png



#15 Andreas Jonsson   Moderators   -  Reputation: 3444

Like
0Likes
Like

Posted 05 January 2014 - 01:11 PM

I've checked in these changes in revision 1807.

 

Thanks,

Andreas


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game




Old topic!
Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.



PARTNERS