(08-03-2011, 04:04 PM)niahoo a écrit : Mais alors pourquoi tu l'appelles exponentialConv ? Ça n'a rien à voir ...
Parce que j'avais pas que ça à faire ^^ Et que quand j'ai commencé à écrire la fonction, je pensais ne faire qu'une conversion de la notation exponentielle. Et au final elle ne fait que cela sans la représentation interne de php.
(08-03-2011, 04:04 PM)niahoo a écrit : mais je n'ai pas compris l'avantage par rapport à sprintf
Faudrait peux-être tester ta solution pour y voir le désavantage non ?
$number = 1.7682711283366E-6;
var_dump(sprintf('%f', $number)); // string(8) "0.000002"
var_dump(sprintf('%F', $number)); // string(8) "0.000002"
Citation :Floating point numbers have limited precision. Although it depends on the system, PHP typically uses the IEEE 754 double precision format, which will give a maximum relative error due to rounding in the order of 1.11e-16. Non elementary arithmetic operations may give larger errors, and, of course, error progragation must be considered when several operations are compounded.http://php.net/manual/en/language.types.float.php
Additionally, rational numbers that are exactly representable as floating point numbers in base 10, like 0.1 or 0.7, do not have an exact representation as floating point numbers in base 2, which is used internally, no matter the size of the mantissa. Hence, they cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9999999999999991118....
So never trust floating number results to the last digit, and never compare floating point numbers for equality. If higher precision is necessary, the arbitrary precision math functions and gmp functions are available.