• Sun 2019.08.11

    http://www.espruino.com/Reference#l_Math­_round

    https://developer.mozilla.org/en-US/docs­/Web/JavaScript/Reference/Global_Objects­/Math/round
    "If the fractional portion of the argument is greater than 0.5, the argument is rounded to the integer with the next higher absolute value. If it is less than 0.5, the argument is rounded to the integer with the lower absolute value. If the fractional portion is exactly 0.5, the argument is rounded to the next integer in the direction of +8. Note that this differs from many languages' round() functions, which often round this case to the next integer away from zero, instead giving a different result in the case of negative numbers with a fractional part of exactly 0.5."


    While rounding towards positive infinity does work for negative numbers, it is not rounding
    correctly for exact 0.5 values.

    >console.log(Math.round(-100.6), Math.round(-100.4), Math.round(-101.5), Math.round(-100.5));
    -101 -100 -101 -100
    =undefined
    
    >console.log(Math.round(100.6), Math.round(100.4), Math.round(101.5), Math.round(100.5));
    101 100 101 100
    =undefined
    >
    


    Correct values
    > -101 -100 -101 -100
    > 101 100 102 101
    


    >process.env
    ={
      VERSION: "2v04",
      GIT_COMMIT: "3956264e",
      BOARD: "ESPRUINOWIFI",
    



    EDIT:

    Had a thought, could this anomaly be related to the floating point number of digits to right of zero not matching different browsers and node.js output? hmmmm. . . .

    http://forum.espruino.com/conversations/­336605/
    test files #1



    EDIT: Tue 2019.08.20

    see snippet that may be helpful in resolving this
    http://forum.espruino.com/comments/14867­790/

  • @Robin

    If you like take a look at the source code to find and fix the error ;-)

  • Or it it might be related to this issue

    https://github.com/espruino/Espruino/iss­ues/1573

  • Just to add:

    $ ./espruino
    >(new Float64Array([101.5])).buffer
    =new Uint8Array([0, 0, 0, 0, 0, 96, 89, 64]).buffer
    
    $ node
    > (new Float64Array([101.5])).buffer
    ArrayBuffer { byteLength: 8 }
    > new Uint8Array((new Float64Array([101.5])).buffer)
    Uint8Array [ 0, 0, 0, 0, 0, 96, 89, 64 ]
    

    So this would appear not to be a parsing issue (like 1573) but is to do with the rounding code itself

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Math.round() doesn't follow specification for exact 0.5

Posted by Avatar for Robin @Robin

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