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Machine Constants in Javascript?

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Join Date: Jul 2006

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DavidB

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Machine Constants in Javascript?

Jun 1st, 2007

I am presently translating some code from C++ to Javascript and it involves quite a few floating point calculations. The program uses several built-in machine constants to help it quantify and limit computer round-off error. For example, it includes the constants DBL_MIN and DBL_EPSILON from the <cfloat> library within C++.

I am now wondering: does Javascript offer these constants as built-in values too? I suppose I could calculate them myself, by brute force, but if these values are already available, it would help me keep the Javascript version shorter.

Does Javascript provide built-in, comparable values for DBL_MIN and DBL_EPSILON? (If so, how do I access them?)

Regards.

David

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Join Date: Jun 2006

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~s.o.s~

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Failure as a human

Re: Machine Constants in Javascript?

Jun 3rd, 2007

You can always peek into the header files of the compiler you are using to find out the value of those in-built constants and put the same in a JS file and include that file.

Something like:

 Help with Code Tags 
 javascript Syntax (Toggle Plain Text) 
// Vars.js
var DB_EPSILON = 0.00000000123
var DB_MIN = 0.125
// Vars.js
var DB_EPSILON = 0.00000000123
var DB_MIN = 0.125

Help with Code Tags

javascript Syntax (Toggle Plain Text)

<html>
<head>
  <script src="Vars.js"></script>
</head>
<body>
<!-- code -->
</body>
</html>

Last edited by ~s.o.s~; Jun 3rd, 2007 at 1:53 pm.

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Join Date: Jan 2007

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MidiMagic

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Re: Machine Constants in Javascript?

Jun 5th, 2007

If you want to know the actual minimum value of the smallest value the current running JavaScript can actually use, it will tell you.

Use: Number.MIN_VALUE

JS provides the following constants:

Number.MIN_VALUE:
The smallest positive value which can be stored. It is close to 5E-324

Number.MAX_VALUE:
The largest positive value which can be stored. It is close to 1.79E+308

Number.NEGATIVE_INFINITY:
Returns the internal representation for negative infinity

Number.POSITIVE_INFINITY:
Returns the internal representation for positive infinity

Math.E:
Returns the natural base.

Math.LN10:
Returns the natural log of 10.

Math.LN2:
Returns the natural log of 2.

Math.LOG10E:
Returns the common log of the natural base.

Math.LOG2E:
Returns the binary-base log of the natural base.

Math.PI:
Returns the value of pi.

Math.SQRT1_2:
Returns the square root of one half.

Math.SQRT2:
Returns the sqiare root of 2.

Last edited by MidiMagic; Jun 5th, 2007 at 5:04 pm. Reason: too fat

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