"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
      You might have more luck with:
      outlet(0, Math.round(myOutput));
      or
      outlet(0, Math.floor(myOutput));
      The problem is just that JavaScript doesn't have integers, what a wonderful world ;-)
    • Sep 20 2013 | 4:10 pm
      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
    • Sep 20 2013 | 7:24 pm
      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.
    • Sep 20 2013 | 8:20 pm
      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