Subj : Re: C64 BASIC - what's faster INT() or %? Plus benefits of DEF FN A()
To   : Holger
From : Charles Richmond
Date : Mon May 07 2018 14:06:45

On 4/19/2018 6:21 AM, Holger wrote:
> Am 17.04.2018 um 04:46 schrieb John H. Guillory:
>>   SB> For clarification, which is faster?
>>   SB> 10 X=INT(64*RND(0)+1)
>>   SB> or
>>   SB> 10 X%=64*RND(0)+1
>>
>> Just guessing, I'd say the second one, or 10 X%=64*RND(0)+1
>> because in the first, your converting 64*RNND(0)+1 to an integer, then
>> converting back to a single precision decimal point value.
>>
> Effectively, calculations always happen in floating point, and INT()
> returns a FP value in the floating point accu. Conversion will take
> place on assignment to the destination variable. The INT() operation is
> similar to the truncation operation to fit the FP accu value into X%.
> In fact, the major difference is that the first line has to copy 5 bytes
> into a variable space and the second will copy 2 bytes.
>
> There isn't even an advantage in space requirement for the variable;
> both need 7 bytes, i.e. 2 bytes for the name (like A1 or B2% or C3$) and
> 5 for the value; an integer variable just wastes 3 bytes for the value.
> It is different for integer vs. float arrays; in this case a % value is
> indeed packed into 2 bytes.
>

I am *not* sue about CBM, but C=64 BASIC does all its arithmetic in
floating point.  That means if you have a line like:

120 X% = A% * B%

....this forces the interpreter to *convert* A% and B% to floating point,
then do the multiplication using the floating point routines, then
convert the answer back to an integer and store the answer in X%.  Not
very efficient to do...


--
numerist at aquaporin4 dot com

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