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Asked: 2026-05-12T19:32:57+00:00

Hey all, let’s jump straight to a code sample to show how ECMAScript/JavaScript/AS3 can’t

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Hey all, let’s jump straight to a code sample to show how ECMAScript/JavaScript/AS3 can’t do simple math right (AS3 uses a ‘IEEE-754 double-precision floating-point number’ for the Number class which is supposedly identical to that used in JavaScript)…

trace(1.1);         //'1.1': Ok, fine, looks good.
trace(1.1*100);     //'110.00000000000001': What!?
trace((1.1*100)/100);  //'1.1': Brings it back to 1.1 (since we're apparently multiplying by *approximately* 100 and then dividing by the same *approximate* '100' amount)
trace(1.1*100-110); //'1.4210854715202004e-14': Proof that according to AS3, 1.1*100!=110 (i.e. this isn't just a bug in Number.toString())
trace(1.1*100==110);   //'false': Even further proof that according to AS3, 1.1*100!=110

What gives?

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1 Answer

  1. Editorial Team

    Welcome to the wonderful world of floating point calculation accuracy. In general, floating point calculations will give you results that are very very nearly correct, but comparing outputs for absolute equality is unlikely to give you results you expect without the use of rounding functions.

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