Is it possible to do a Bitwise AND in SDL?

I can't find the word 'bit' anywhere in the help file, maybe I'm missing an
obvious synonym?

I want to test a series of bit flags, i.e.
#local myvar=13;

#if (myvar && 1)
   //do bit flag 1 stuff
#end


        == John ==

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> Is it possible to do a Bitwise AND in SDL?

I'm pretty sure that's not possible. :-(

You can of course do stuff with the MOD() function to achive vaguely the 
same effect, but I don't think POV-Ray lets you do it directly.

Andrew @ home.

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John D. Gwinner <joh### [at] cornelledu> wrote:
> Is it possible to do a Bitwise AND in SDL?

  POV-Ray handles only flotaing point numbers.
  Even though you can more or less simulate bit flags with floating
point numbers, it's not very feasible. And certainly there are no
bit operators for them.

  Just use an array for your flags. It may take more memory, but you
are not having millions of flags, are you?-)

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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>   Just use an array for your flags. It may take more memory, but you
> are not having millions of flags, are you?-)

Actually, just thought I'd mention... I tried doing this with strings 
instead. (e.g., Flags = "zNcv" means only the Z-flag is set.)

I was then shocked to find that
   #if (Flag = "Z")
gives me an error... it was later pointed out that
   #if (asc(Flag) = asc("Z"))
works just fine. Weird... Anyway, I went this way because "nCV" is more 
instantly understandable than 0x03. ;-) Just a thought...

Andrew @ home.

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In article <406f258e@news.povray.org>, war### [at] tagpovrayorg says...
> John D. Gwinner <joh### [at] cornelledu> wrote:
> > Is it possible to do a Bitwise AND in SDL?
> 
>   POV-Ray handles only flotaing point numbers.
>   Even though you can more or less simulate bit flags with floating
> point numbers, it's not very feasible. And certainly there are no
> bit operators for them.
> 
>   Just use an array for your flags. It may take more memory, but you
> are not having millions of flags, are you?-)
> 
> 
But.... Some mathematical operations require such operations.... Or at 
least they can use them, so it is odd that such a thing is not actually 
supported. Any method used to simulate this, where the result needs to be 
used as a real numeric value would take extra steps to 'build' the value 
from the array, string or whatever. This is imho quite silly.

-- 
void main () {

    call functional_code()
  else
    call crash_windows();
}

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> But.... Some mathematical operations require such operations.... Or at
> least they can use them, so it is odd that such a thing is not actually
> supported. Any method used to simulate this, where the result needs to be
> used as a real numeric value would take extra steps to 'build' the value
> from the array, string or whatever. This is imho quite silly.

True. But it would be possible. POV-Ray SDL is just a simple scripting
language provided for convenience; if you really need the speed that bit
operations can give you, then you're *probably* using the wrong language for
the job. You should consider writing a program in a different language which
outputs a POV-Ray SDL file which can be #included from your main one, to
provide the necessary data or objects.

 - Slime
 [ http://www.slimeland.com/ ]

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Patrick Elliott <sha### [at] hotmailcom> wrote:
> But.... Some mathematical operations require such operations....

  Which ones for example?

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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In article <407004ff@news.povray.org>,
 Andrew C on Mozilla <voi### [at] devnull> wrote:

> I was then shocked to find that
>    #if (Flag = "Z")
> gives me an error... it was later pointed out that
>    #if (asc(Flag) = asc("Z"))
> works just fine. Weird... Anyway, I went this way because "nCV" is more 
> instantly understandable than 0x03. ;-) Just a thought...

The equality operator expects numeric values, which strings aren't. Not 
so weird, though scripting languages usually have better built-in 
support for strings, POV Script isn't intended to do much string 
processing. Anyway, that's an odd way of comparing strings, and only 
works for single characters. This is the usual method:

#if(strcmp(Flag, "Z") = 0)

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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In article <MPG.1ada23538462981989a0c@news.povray.org>,
 Patrick Elliott <sha### [at] hotmailcom> wrote:

> But.... Some mathematical operations require such operations.... Or at 
> least they can use them, so it is odd that such a thing is not actually 
> supported. Any method used to simulate this, where the result needs to be 
> used as a real numeric value would take extra steps to 'build' the value 
> from the array, string or whatever. This is imho quite silly.

It is not silly. The scene language is a high level language, and has no 
concept of bits, or even integers. Its numeric values are double 
precision floats. Performing bitwise operations on these is generally a 
bad idea, and is rarely useful. These operations are rarely used, and 
nearly useless for POV-Ray scripts.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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> Is it possible to do a Bitwise AND in SDL?

Yes, but not directly. Also note, that, as Warp pointed out, pov numbers
are floating point, so you might lose some bits if you use too many.

Untested suggestion:

// to extract bit K of N:

#macro Bit(K,N)
   ((floor(N/pow(2,K))) mod 2)
#end

// bitwise operations with K bits

#macro Not(N,K)
   pow(2,K)-1-N
#end

#macro Nand(N,M,K)
   #local I=0;
   #local R=0;
   #while (I<K)
     #local R = R+(1-Bit(I,N)*Bit(I,M))*pow(2,I);
     #local I = I+1;
   #end
   (R)
#end

#macro And(N,M,K)
   Not(Nand(N,M,K),K)
#end

#macro Or(N,M,K)
   Nand(Not(N,K),Not(M,K),K)
#end

#macro Xor(N,M,K)
   And(Or(N,M,K),Nand(N,M,K),K)
#end


-- 
merge{#local i=-11;#while(i<11)#local
i=i+.1;sphere{<i*(i*i*(.05-i*i*(4e-7*i*i+3e-4))-3)10*sin(i)30>.5}#end
pigment{rgbt 1}interior{media{emission x}}hollow}//  Mark Weyer

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