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virtual base classes in c++

Mateusz Małczak2007-02-21c++comments

ive written short piece of code... but it didnt worked. i must write this code down somewhere. im almost sure that next time i will have to deal with virtual inheritance in c++ i will make this mistake once again. lets take a look at this few lines of code : 

class A { ... }
class B : public virtual A 
{ 
 B( void ) : A( void ){ ... }
}
class C : public B 
{
 C( void ) : B(void ){ ... }
}
what is wrong ? ive asked myself
well... C class constructor should also invoke direct call to class A constructor. bleh... thats easy, isnt that... not for me hehe

swf format - note 1 (swf tags)

Mateusz Małczak2007-02-19swfcomments

SWF in open format used by Flash.
swf file format documentation can be freely downloaded from adobe homepage. below ive listed all tags that can be used in swf file. tag value
0 end
1 ShowFrame
2 DefineShape
3 -
4 PlaceObject
5 RemoveObject
6 DefineBits
7 DefineButton
8 JPEGTables
9 SetBackgroundColor
10 DefineFont
11 DefineText
12 DoAction
13 DefineFontInfo
14 DefineSound
15 StartSound
16 -
17 DefineButtonSound
18 SoundStreamHead
19 SoundStreamBlock
20 DefineBitsLossless
21 DefineBitsJPEG2
22 DefineShape2
23 DefineButtonCxform
24 Protect
25 -
26 PlaceObject2
27 -
28 RemnoveObject2
29 -
30 -
31 -
32 DefineShape3
33 DefineText2
34 DefineButton2
35 DefineBitsJPEG3
36 DefineBitsLossless2
37 DefineEditText
38 -
39 DefineSprite
40 -
41 -
42 -
43 FrameLabel
44 -
45 SoundStreamHead2
46 DefineMorphShape
47 -
48 DefineFont2
49 -
50 -
51 -
52 -
53 -
54 -
55 -
56 ExportAssets
57 ImoprtAssets
58 EnableDebugger
59 DoInitAction
60 DefineVideoStream
61 VideoStream
62 DefineFontInfo2
63 -
64 EnableDebugger2
65 ScriptLimits
66 SetTabIndex

skull fractal & XaoS

Mateusz Małczak2007-02-09fractalscomments

recently ive been developing my port of XaoS fractal zoomer with skull fractal added to it. but... direct usage of skull fractal formula had given me quite poor effect, XaoS turned to be verrrry slow. and that was unacceptable ! to make it fast again i had to play with mathematics to get equivalent but faster to calculate skull fractal formula. ive started with skull fractal formula

img11.gif
in computations, the most expensive part of this formula are hiperbolic functions (for further details on calculations of hiperbolic functions with complex arguments go here). after some time i came up with formula of form
img21.gif
now we have to do less trigonometric calculations. what is most important, sine and cosine functions of the same real number can be evaluated in just one step using fpu instruction fsincos. using good implementation we can use this trick also with hiperbolic functions. but its not enough, because we can still do some further simplifications. which are related with arguments of used trigonometric functions. as we can see above, we have addition or subtraction of two complex numbers defined in skull fractal formula. in our case it is easy to show that these two operations can be expressed as :
img3.gif
there cis(a)=cos(a)+isin(a). After shown operations my XaoS port rendered skull fractal much faster.

Determinant

Mateusz Małczak2007-02-07mathcomments

determinant is the function that associates a scalar value det(A) to the square nxn matrix A.in computer computations it can be easily computated using LU matrix decomposition. but, ive made "quick and dirty" implementation of matrix determinant definition, just to see how it works. just to refresh memory, determinant of square nxn matrix A can be expressed using determinant expansion by minors :

img1.gif
where Cij is called cofactor, and Mij is so-called minor of matrix A. Minor is obtained by taking the determinant of matrix A with out i-th row ant j-th column.
img2.gif
there is no sumation over j index, as it can be chosen freely. we see now that calculation of matrix determinant can be implemented (in very naive approach) using recursive function. as we are calculating matrix determinant using recursion (and/or iterations) we are intrested in aswering the quaestion, who many matrices have to be created (including input matrix and 1x1 matrices) ?
matrix size : 2x2 matrices count : 3
matrix size : 3x3 matrices count : 10
matrix size : 4x4 matrices count : 41
matrix size : 5x5 matrices count : 206
.
matrix size : 8x8 matrices count : 69281
.
matrix size : 10x10 matrices count : 6235301
matrix size : 11x11 matrices count : 68588312
code of my "quick and dirty" can be taken from here : det.c

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