For some values, such as "10152116260776319", casting to number with parseFloat or Number("***") methods increments the original value by 1.
Number("10152116260776319") => 10152116260776320
Number("10202784509328139") => 10202784509328140
Is there any way to fix this? Or do I need to update all of my code to Strings.
Thanks in advance.
The issue is not due to a problem with parseFloat or Number("***"), but a limitation of the Number type. Basically, the Number type can only hold integers properly if they're below 253 (9,007,199,254,740,992), because they're double precision floating point numbers (check out this Wikipedia page for more details: http://en.wikipedia.org/wiki/Double-precision_floating-point_format)
The problem occurs even without casting, for example
var val1:Number = 9007199254740990;
var val2:Number = 9007199254740991;
var val3:Number = 9007199254740992;
var val4:Number = 9007199254740993;
var val5:Number = 9007199254740994;
var val6:Number = 10152116260776319;
trace(val1); // 9007199254740990
trace(val2); // 9007199254740991
trace(val3); // 9007199254740992
trace(val4); // 9007199254740992
trace(val5); // 9007199254740994
trace(val6); // 10152116260776320
If you really need to store integers that large, someone's made a BigInt class that you can use: http://as3asclublib.googlecode.com/svn-history/r29/trunk/data/BigInt.as
Related
This question relates to an animated map template which we have developed at the UKs Office for National Statistics. It has been applied to many datasets and geographies many uses without problem. For example,
http://www.ons.gov.uk/ons/interactive/vp3-census-map/index.html
http://www.statistica.md/pageview.php?l=ro&idc=390&id=3807
The .fla calls on a supporting .as file (see below) to introduce a thousand separator (in the UK a comma, in Germany a full stop (period) defined elsewhwere.
However, the dataset I am currently mapping has large negative values, and it tutrns out that the ORIGINAL HELPER FUNCTION below does not like negative values with 3, 6, 9 or 12 (etc) digits.
-100 to -999 for instance are rendered NaN,100 to NaN,999.
This is because such values are recognised as being 4 digits long. They are being split, the comma introduced, and the -ve sign is misunderstood.
I reckon the approach must be to use absolute values, add in the comma and then (for the negative values) add the -ve sign back in afterwards. But so far, trials of the ADAPTED HELPER FUNCTION have produced only error. :-(
Can anyone tell me how to put the -ve sign back in , please?
Many thanks.
Bruce Mitchell
==================================================================================
//ORIGINAL HELPER FUNCTION: ACCEPTS A NUMBER AND RETURNS A STRING WITH THOUSANDS SEPARATOR ATTACHED IF NECESSARY
function addThouSep(num) {
/*
a. Acquire the number - 'myTrendValue' or 'myDataValue' - from function calcValues
b. Record it (still as a number) to data precision.
1. Turn dataORtrend into a string
2. See if there is a decimal in it.
3. If there isn't, just run the normal addThouSep.
4. If there is, run addThouSep just on the first bit of the string - then add the decimal back on again at the end.
*/
var myNum:Number = correctFPE(num); // Create number variable myNum and populate it with 'num'
// (myTrendvalue or myData Value from calcValues function) passed thru 'correctPFE'
var strNum:String = myNum+""; // Create string version of the dataORtrend number - so instead of 63, you get '63'
var myArray = strNum.split("."); // Create array representing elements of strNum, split by decimal point.
//trace(myArray.length); // How long is the array?
if (myArray.length==1) { // Integer, no decimal.
if (strNum.length < 4)//999 doesn't need a comma.
return strNum;
return addThouSep(strNum.slice(0, -3))+xmlData.thouSep+strNum.slice(-3);
}
else { // Float, with decimal
if (myArray[0].length < 4)//999 doesn't need a comma
return strNum;
return (addThouSep(myArray[0].slice(0, -3))+xmlData.thouSep+myArray[0].slice(-3)+"."+myArray[1]);
}
}
==================================================================================
//ADAPTED HELPER FUNCTION: ACCEPTS A NUMBER AND RETURNS A STRING WITH THOUSANDS SEPARATOR ATTACHED IF NECESSARY
function addThouSep(num) {
/*
a. Acquire the number - 'myTrendValue' or 'myDataValue' - from function calcValues
b. Record it (still as a number) to data precision.
1. Turn dataORtrend into a string
2. See if there is a decimal in it.
3. If there isn't, just run the normal addThouSep.
4. If there is, run addThouSep just on the first bit of the string - then add the decimal back on again at the end.
*/
var myNum:Number = correctFPE(num); // Create number variable myNum and populate it with 'num'
// (myTrendvalue or myData Value from calcValues function) passed thru 'correctPFE'
var myAbsNum:Number = Math.abs(myNum); // ABSOLUTE value of myNum
var strNum:String = myAbsNum+""; // Create string version of the dataORtrend number - so instead of 63, you get '63'
var myArray = strNum.split("."); // Create array representing elements of strNum, split by decimal point.
//trace(myArray.length); // How long is the array?
if (myNum <0){ // negatives
if (myArray.length==1) { // Integer, no decimal.
if (strNum.length < 4)//999 doesn't need a comma.
return strNum;
return addThouSep(strNum.slice(0, -3))+xmlData.thouSep+strNum.slice(-3);
}
else { // Float, with decimal
if (myArray[0].length < 4)//999 doesn't need a comma
return strNum;
return (addThouSep(myArray[0].slice(0, -3))+xmlData.thouSep+myArray[0].slice(-3)+"."+myArray[1]);
}
}
else // positive
if (myArray.length==1) { // Integer, no decimal.
if (strNum.length < 4)//999 doesn't need a comma.
return strNum;
return addThouSep(strNum.slice(0, -3))+xmlData.thouSep+strNum.slice(-3);
}
else { // Float, with decimal
if (myArray[0].length < 4)//999 doesn't need a comma
return strNum;
return (addThouSep(myArray[0].slice(0, -3))+xmlData.thouSep+myArray[0].slice(-3)+"."+myArray[1]);
}
}
==================================================================================
If you're adding commas often (or need to support numbers with decimals) then you may want a highly optimized utility function and go with straightforward string manipulation:
public static function commaify( input:Number ):String
{
var split:Array = input.toString().split( '.' ),
front:String = split[0],
back:String = ( split.length > 1 ) ? "." + split[1] : null,
pos:int = input < 0 ? 2 : 1,
commas:int = Math.floor( (front.length - pos) / 3 ),
i:int = 1;
for ( ; i <= commas; i++ )
{
pos = front.length - (3 * i + i - 1);
front = front.slice( 0, pos ) + "," + front.slice( pos );
}
if ( back )
return front + back;
else
return front;
}
While less elegant it's stable and performant — you can find a comparison suite at my answer of a similar question https://stackoverflow.com/a/13410560/934195
Why not use something simple like this function I've made?
function numberFormat(input:Number):String
{
var base:String = input.toString();
base = base.split("").reverse().join("");
base = base.replace(/\d{3}(?=\d)/g, "$&,");
return base.split("").reverse().join("");
}
Tests:
trace( numberFormat(-100) ); // -100
trace( numberFormat(5000) ); // 5,000
trace( numberFormat(-85600) ); // -85,600
Explanation:
Convert the input number to a string.
Reverse it.
Use .replace() to find all occurrences of three numbers followed by another number. We use $&, as the replacement, which basically means take all of those occurences and replace it with the value we found, plus a comma.
Reverse the string again and return it.
Did you try using the built in Number formatting options that support localized number values:
Localized Formatting with NumberFormatter
I am sorry if this is a beginner's question.
I made some Arrays named like map01, map02 and so on... As you can see, I'm making a tile-based flash here. And I need to make a function that when you input a number like: createmap(1); it will get the variable map01 and use the information.
Can I do anything like: var temp:Array = Array(["map" + valueInput]);??
Please tell me if you need anything more.
First, instead of having variables with indices in their names, you should create an array of them. Here, an array of arrays.
So you just have to call var temp:Array = maps[valueInput] as Array;.
If you really don't want to do that and stick with your n variables, you can write
var index:String = valueInput.toString();
if (index.length == 1)
index = "0" + index; //have the index on two digits "01", "02"
var temp:Array = this["map" + index];
Note that it will only work for your 99 first variables (oh God...)
I guess a step back is in order. My original question is at the bottom of this post for reference.
I am writing a word guessing game and wanted a way to:
1. Given a word length of 2 - 10 characters, randomly generate a valid english word to guess
2.given a 2 - 10 character guess, ensure that it is a valid english word.
I created a vector of 9 objects, one for each word length and dynamically created 172000
property/ value pairs using the words from a word list to name the properties and setting their value to true. The inner loop is:
for (i = 0; i < _WordCount[wordLength] - 2; i)
{
_WordsList[wordLength]["" + _WordsVector[wordLength][i++]] = true;
}
To validate a word , the following lookup returns true if valid:
function Validate(key:String):Boolean
{
return _WordsList[key.length - 2][key]
}
I transferred them from a vector to objects to take advantage of the hash take lookup of the properties. Haven't looked at how much memory this all takes but it's been a useful learning exercise.
I just wasn't sure how best to randomly choose a property from one of the objects. I was thinking of validating whatever method I chose by generating 1000 000 words and analyzing the statistics of the distribution.
So I suppose my question should really first be am I better off using some other approach such as keeping the lists in vectors and doing a search each time ?
Original question
Newbie first question:
I read a thread that said that traversal order in a for.. in is determined by a hash table and appears random.
I'm looking for a good way to randomly select a property in an object. Would the first element in a for .. in traversing the properties, or perhaps the random nth element in the iteration be truly random. I'd like to ensure that there is approximately an equal probability of accessing a given property. The Objects have between approximately 100 and 20000 properties. Other approaches ?
thanks.
Looking at the scenario you described in your edited question, I'd suggest using a Vector.<String> and your map object.
You can store all your keys in the vector and map them in the object, then you can select a random numeric key in the vector and use the result as a key in the map object.
To make it clear, take a look at this simple example:
var keys:Vector.<String> = new Vector.<String>();
var map:Object = { };
function add(key:String, value:*):void
{
keys.push(key);
map[key] = value;
}
function getRandom():*
{
var randomKey = keys[int(Math.random() * keys.length)];
return map[randomKey];
}
And you can use it like this:
add("a", "x");
add("b", "y");
add("c", "z");
var radomValue:* = getRandom();
Using Object instead of String
Instead of storing the strings you can store objects that have the string inside of them,
something like:
public class Word
{
public var value:String;
public var length:int;
public function Word(value:String)
{
this.value = value;
this.length = value.length;
}
}
Use this object as value instead of the string, but you need to change your map object to be a Dictionary:
var map:Dictionary = new Dictionary();
function add(key:Word, value:*):void
{
keys.push(key);
map[key] = value;
}
This way you won't duplicate every word (but will have a little class overhead).
I have a function that gets a numeric value (as Object) and returns a well formatted representation of that number. Because we can get very small numbers, in the process we use the Number object of flex. this is part of the code:
var numericValue:Number = Number(value.toString());
var fixed:String = numericValue.toFixed(precision);
This is the problem: there are situations that the numeric value is in the form of
5.684341886080802e-14
because we want to represent these numbers as 0 we use the above code. In this specific case, where precision is 0 we get an odd result
Initial Values:
value = 5.684341886080802e-14
percision = 0
Operation on values:
var numericValue:Number = Number(value.toString());
var fixed:String = numericValue.toFixed(precision);
Result:
fix = "1."
Why is this?
(BTW - on other numbers in the representataion of X.XXXXXXe-YY with percision bigger than 0 we get the correct result of 0)
This is a bug in Flash Player (FP-5141). It has been around for quite a while. The bug report says it is fixed, but it is not as of Flash Player 11.5.
I have a textInput control that sends .txt value to an array collection. The array collection is a collection of US zip codes so I use a regular expression to ensure I only get digits from the textInput.
private function addSingle(stringLoader:ArrayCollection):ArrayCollection {
arrayString += (txtSingle.text) + '';
var re:RegExp = /\D/;
var newArray:Array = arrayString.split(re);
The US zip codes start at 00501. Following the debugger, after the zip is submitted, the variable 'arrayString' is 00501. But once 'newArray' is assigned a vaule, it removes the first two 0s and leaves me with 501. Is this my regular expression doing something I'm not expecting? Could it be the array changing the value? I wrote a regexp test in javascript.
<script type="text/javascript">
var str="00501";
var patt1=/\D/;
document.write(str.match(patt1));
</script>
and i get null, which leads me to believe the regexp Im using is fine. In the help docs on the split method, I dont see any reference to leading 0s being a problem.
**I have removed the regular expression from my code completely and the same problem is still happening. Which means it is not the regular expression where the problem is coming from.
Running this simplified case:
var arrayString:String = '00501';
var re:RegExp = /\D/;
var newArray:Array = arrayString.split(re);
trace(newArray);
Yields '00501' as expected. There's nothing in the code you've posted that would strip leading zeros. You may want to dig around a bit more.
This smells suspiciously like Number coercion: Number('00501') yields 501. Read through the docs for implicit conversions and check if any pop up in your code.
What about this ?
/^\d+$/
You can also specify exactly 5 numbers like this :
/^\d{5}$/
I recommend just getting the zip codes instead of splitting on non-digits (especially if 'arrayString' might have multiple zip codes):
var newArray:Array = [];
var pattern:RegExp = /(\d+)/g;
var zipObject:Object;
while ((zipObject = pattern.exec(arrayString)) != null)
{
newArray.push(zipObject[1]);
}
for (var i:int = 0; i < newArray.length; i++)
{
trace("zip code " + i + " is: " + newArray[i]);
}