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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: function to get frequencies of a char array
Date: Tue, 27 Jan 2015 14:50:58 +0100
Organization: PointedEars Software (PES)
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Christoph M. Becker wrote:

> Thomas 'PointedEars' Lahn wrote:
>> Christoph M. Becker wrote:
>>> Evertjan. wrote:
>>>> This was about a count,
>>>> in Javascript you cannot
>>>> in a single variable
>>>> count from 0 to 1e32
>>>> for reasons of […] resolution.
>>>
>>> […]
>>>  However, I don't understand what you mean by "resolution".
>> 
>> [limits of IEEE 754 doubles’ integer precision]
> 
> Thanks for the explanation.

You’re welcome.

> Actually, I screwed up again, as I meant 2³² (not 10³²), which can be
> represented exactly as integer, but doesn't "survive" the ToInt32()
> call.  Even 2³¹ does not:
> 
>   Math.pow(2, 31) | 0 // => -2147483648

Correct.  I suspected something was wrong with using “| 0” there, but had 
not found the time to investigate it.  Thanks.

I have also stated that I would not use Array.prototype.reduce() to return a 
non-primitive value.  It is possible that judgement was incorrect.  It is 
rather fascinating to obtain a character (or word) statistics¹ of an HTML 
document (or any other text) – confirming, for example, that “e” usually is 
the most frequent letter –, just by typing

  document.body.textContent.split("").reduce(function (prev, curr) {
    prev[curr] = (prev[curr] || 0) + 1;
    return prev;
  }, Object.create(null));

as one line into the script console.

______
¹  it is possible to split() using a regular expression like /\s+/

> As we were talking about array *indexes*[1], values equal to or beyond
> 2³² are irrelevant, anyway.
> 
> [1] <news:2697158.aGRKFDBAEn@PointedEars.de>

I do not follow.  In

|  if (e) { counts[e] ? ++counts[e] : (counts[e] = 1); }

as cited, “e” is not an array index.

-- 
PointedEars
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