Re: [PHP-ES] Problema con una simple suma ...

Se me ocurre que puede ser cosa de simple redondeo. Es decir, reduzcamos
decimales.

Si coges el valor 0,09 y pones solo 1 decimal, normalmente te devuelve 0,1.
Si lo haces con 0,099 y 2 decimales, te seguirá diciendo 0,1, con 3 0,99
...
creo que es lo mismo que te pasa a ti solo que con 14 decimales.




2010/4/9 hackob <[email protected]>

> Curiosamente con un valor de 14 sigo con el problema, sin embargo si subo a
> 15 da el resultado esperado.
>
> Gracias
> @hackob
> hackob [ [email protected] ]
>
> -----Original Message-----
> From: "J. Mauro Daino" <[email protected]>
> Date: Thu, 8 Apr 2010 21:18:25
> To: php-list<[email protected]>
> Subject: Re: [PHP-ES] Problema con una simple suma ...
> Hola hackob:
>
> 2010/4/8 hackob <[email protected]>
>
> > El problema se solucionó cuando modifiqué el parámetro precision en el
> > php.ini de 12 a 15, lo curioso es que si pongo 16 el resultado es
> > 0.099999999999999998.
> >
> > Me gustaría saber el por qué ...
> >
>
> Copio y pego desde http://php.net/manual/en/language.types.float.php:
>
> The size of a float is platform-dependent, although a maximum of ~1.8e308
> with a precision of roughly 14 decimal digits is a common value (the 64 bit
> IEEE format).
> *Warning*Floating point precision
>
> It is typical that simple decimal fractions like *0.1* or *0.7* 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 *7.9*.
>
> 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*.
>
> 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 <http://php.net/manual/en/ref.bc.php> and
> gmp<http://php.net/manual/en/ref.gmp.php> functions
> are available.
> O sea, si queres una suma de precisión no uses el operador "+" sino la
> función "bcadd()" o "gmp_add()". Suerte.
>
> --
> J. Mauro Daino (tcc: jMd)
> * profile: google.com/profiles/maurodaino
>
>