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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.lang.javascript
Subject: Re: IE and IEE 754
Date: Fri, 29 Aug 2014 12:39:28 +0100
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"Evertjan." <exxjxw.hannivoort@inter.nl.net> writes:

> Ben Bacarisse <ben.usenet@bsb.me.uk> wrote on 29 aug 2014 in 
> comp.lang.javascript:
>
>> "Evertjan." <exxjxw.hannivoort@inter.nl.net> writes:
>> 
>>> Ben Bacarisse <ben.usenet@bsb.me.uk> wrote on 28 aug 2014 in 
>>> comp.lang.javascript:
>>>> You mean "yes, but..." surely?  You did not say that that they cannot be
>>>> *trusted* to be exact, you said that they can't ever be exact.
>>>
>>> Wow, are you still in kindergarten?
>> 
>> I'd like to try to unravel this.  I don't think I am wrong to say that
>> 0.5 can be converted to a binary floating point value exactly, and I
>> don't think you disagree on that point, but can you see that what you
>> wrote:
>> 
>>   "... the binary converions of floting point fractional decimal values
>>   NEVER can be right"
>> 
>> does seem to suggest otherwise?  I even suggested that there was a
>> communication problem:
>> 
>>   "What about 0.5 or 0.25?  Why can't these ever be right?  Did you mean
>>   that *all* decimal fractions can't be correctly converted?  That's
>>   certainly the case.  The way you worded it sounds like none of them
>>   can be."
>> 
>> But that was not, it seems, what you wanted to say.
>> 
>> When you rejected my examples of 0.5 and 0.25 you said the conversion
>> could not be trusted to be exact (correct me, if I've misunderstood that
>> as well).  That sounded exactly like a "yes they can be exact, but they
>> can't be trusted to be exact". 
>
> "Fixed point decimal <input> strings" can incidentally be exact, like 
> '27.00', but the whole idea is the you as a programmer, when allowing for 
> fractional input strings[!], don't know beforehand what number will be 
> inputted, and an incidental input of '0.50' cannot be taken as exact, 
> because you would have to make an array of exact decimal values, and still 
> have the rest of the possibilities delt with as non-exact.
>
> Therefore your example of 0.5 is childish, as it does not seriously address 
> the problem of binary conversion in programmes.

But it's unfair of you to make that accusation when I never intended it
to be anything other than a counter example to what looked like a simple
statement of fact.  I'm sorry you thought I was offering an example that
addressed the general problem of decimal to binary floating point
conversion, but I can't see how you could think I was, especially as I
explicitly suggested that maybe your remark had come over as being more
general than you had intended.

<snip>
-- 
Ben.