"crossing the bridge" with bit accuracy from js to max

Sep 19 2013 | 9:05 pm

Hello, I'm generating bit patterns via javascript to send over the serial port (via serial object). It seems that max interprets all non-string variables as floats, and so I get rounding errors on the output of the js object. Some of these patterns are headers, so need to be bit accurate. I tried an ArrayBuffer to "cast" to Uint32, which works as long as I'm in javascriptland, but max ignores this, and treats it as a float anyway; I try to force it to an int with:

outlet(0, "int", myOutput);

but this rounds the float on the conversion, and changing the bit pattern.

Any ideas for a work-around?

Thanks! Christopher Deckard Seattle, Wa

Sep 20 2013 | 12:44 pm
Emmanuel Jourdan
You might have more luck with:outlet(0, Math.round(myOutput)); oroutlet(0, Math.floor(myOutput));
The problem is just that JavaScript doesn't have integers, what a wonderful world ;-)
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Sep 20 2013 | 4:10 pm
cdeckard
thanks for the reply, Emmanuel. I didn't realize javascript didn't have integers *at all*! So it seems that it's still possible for the .round() and floor() functions to change the bit pattern. But I did realize a work-around using strings that seems to work. At the output, I do the following:
outlet(0, my32BitPattern[0].toString(10));
I then use a "fromSymbol" object afterwards that then feeds a simple javascript msg_int() fn to break it into bytes to finally feed a "serial" object. Works a treat!
Cheers! Chris
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Sep 20 2013 | 7:24 pm
Emmanuel Jourdan
Yeah javascript has Numbers ;-)
I would recommend using Math.floor()/Math.round(). toString is going to convert your Number to a string. JavaScript strings are converted to symbols when going on the Max side, and symbol stick there in memory for ever so you don't want to generate symbols for this.
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Sep 20 2013 | 8:20 pm
cdeckard
that's interesting about the memory persistence, Emmanuel. Does Max have any sort of "clear mem" function? Unless I'm missing something, I don't think floor() or round() will work.
for example, if I load my header bitPattern via:
my32BitPattern[0] = 0xDEADBEEF;
javascript thinks this is -6.259853398707798E18. If I then do a floor() or round(), it will then think it is -7. x 10^18, correct?
wait -- I just thought about this a bit more -- I simply need to use ArrayBuffer to manipulate javascript to treat the number as an integer, then use the floor() function on the way out to max.
Thanks! Christopher Deckard, Seattle
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