The Tor Browser / file revision

 /// Copyright (c) 2012 Ecma International.  All rights reserved. 

 /// Ecma International makes this code available under the terms and conditions set

 /// forth on http://hg.ecmascript.org/tests/test262/raw-file/tip/LICENSE (the 

 /// "Use Terms").   Any redistribution of this code must retain the above 

 /// copyright and this notice and otherwise comply with the Use Terms.

 /**

  * @path ch08/8.5/8.5.1.js

  * @description Valid Number ranges

  */

 // Check range support for Number values (IEEE 754 64-bit floats having the form s*m*2**e)

 //

 // For normalized floats, sign (s) is +1 or -1, m (mantisa) is a positive integer less 

 // than 2**53 but not less than 2**52 and e (exponent) is an integer ranging from -1074 to 971

 //

 // For denormalized floats, s is +1 or -1, m is a positive integer less than 2**52, and

 // e is -1074

 //

 // Below 64-bit float values shown for informational purposes.  Values may be positive or negative.

 // Infinity  >= ~1.797693134862315907729305190789e+308 >= 2**1024

 // MAX_NORM   = ~1.797693134862315708145274237317e+308  = (2**53 - 1) * (2**-52) * (2**1023) = (2**53-1) * (2**971) = (2**1024) - (2**971)

 // MIN_NORM   = ~2.2250738585072013830902327173324e-308 = 2**-1022

 // MAX_DENORM = ~2.2250738585072008890245868760859e-308 = MIN_NORM - MIN_DENORM = (2**-1022) - (2**-1074)

 // MIN_DENORM = ~4.9406564584124654417656879286822e-324 = 2**-1074

 // Fill an array with 2 to the power of (0 ... -1075)

 var value = 1;

 var floatValues = new Array(1076);

 for(var power = 0; power <= 1075; power++){

 	floatValues[power] = value;

     // Use basic math operations for testing, which are required to support 'gradual underflow' rather

     // than Math.pow etc..., which are defined as 'implementation dependent'.

 	value = value * 0.5;

 }

 // The last value is below min denorm and should round to 0, everything else should contain a value

 if(floatValues[1075] !== 0) {

   $ERROR("Value after min denorm should round to 0");

 }

 // Validate the last actual value is min denorm

 if(floatValues[1074] !== 4.9406564584124654417656879286822e-324) {

   $ERROR("Min denorm value is incorrect: " + floatValues[1074]);

 }

 // Validate that every value is half the value before it up to 1

 for(var index = 1074; index > 0; index--){

   if(floatValues[index] === 0){

 	$ERROR("2**-" + index + " should not be 0");

   }

   if(floatValues[index - 1] !== (floatValues[index] * 2)){

 	$ERROR("Value should be double adjacent value at index " + index);

   }

 }

 // Max norm should be supported and compare less than inifity

 if(!(1.797693134862315708145274237317e+308 < Infinity)){

 	$ERROR("Max Number value 1.797693134862315708145274237317e+308 should not overflow to infinity");

 }

 // Numbers closer to 2**1024 then max norm should overflow to infinity

 if(!(1.797693134862315808e+308 === +Infinity)){

 	$ERROR("1.797693134862315808e+308 did not resolve to Infinity");

 }