note 89930 added to language.types.float
| From: | Anonymous at osu1 dot php dot net | Date: | Sun, 29 Mar 2009 16:53:23 +0000 |
| Subject: | note 89930 added to language.types.float | ||
| Groups: | php.notes | ||
| Request: | Send a blank email to php-notes+get-152584@lists.php.net to get a copy of this message | ||
The example, above is good, but the explanation is misleading:
"This is due to the fact that it is impossible to express some fractions in decimal notation
with a finite number of digits. For instance, 1/3 in decimal form becomes 0.3 [repeating]."
What the author *meant* to write is
This is due to the fact that some (most) real numbers cannot be represented with a finite number of
binary digits, or indeed, a finite number of digits in any radix. For example, 1/3 is 0.3333333...
[no vinculum in comment editor!] represented with two significant decimal digits is truncated to
0.33 which is *not* exactly 1/3.
Even this explanation is unsatisfactory, since for any radix other than two (assuming a machine
built on binary logic) we need to represent the significand (mantissa for us old-timers!) itself
with a finite number of binary digits.
So rather than present a good example with a misleading explanation, it would be preferable to
present the same good example with a link to a good explanation, e.g. http://en.wikipedia.org/wiki/Floating_point .
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Server IP: 69.147.83.197
Probable Submitter: 72.208.135.183
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Manual Page -- http://www.php.net/manual/en/language.types.float.php
Edit -- https://master.php.net/note/edit/89930
Del: integrated -- https://master.php.net/note/delete/89930/integrated
Del: useless -- https://master.php.net/note/delete/89930/useless
Del: bad code -- https://master.php.net/note/delete/89930/bad+code
Del: spam -- https://master.php.net/note/delete/89930/spam
Del: non-english -- https://master.php.net/note/delete/89930/non-english
Del: in docs -- https://master.php.net/note/delete/89930/in+docs
Del: other reasons-- https://master.php.net/note/delete/89930
Reject -- https://master.php.net/note/reject/89930
Search -- https://master.php.net/manage/user-notes.php