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<?php
namespace Faker\Provider;
class Biased extends Base
{
/**
* Returns a biased integer between $min and $max (both inclusive).
* The distribution depends on $function.
*
* The algorithm creates two doubles, x ∈ [0, 1], y ∈ [0, 1) and checks whether the
* return value of $function for x is greater than or equal to y. If this is
* the case the number is accepted and x is mapped to the appropriate integer
* between $min and $max. Otherwise two new doubles are created until the pair
* is accepted.
*
* @param int $min Minimum value of the generated integers.
* @param int $max Maximum value of the generated integers.
* @param callable $function A function mapping x ∈ [0, 1] onto a double ∈ [0, 1]
*
* @return int An integer between $min and $max.
*/
public function biasedNumberBetween($min = 0, $max = 100, $function = 'sqrt')
{
do {
$x = mt_rand() / mt_getrandmax();
$y = mt_rand() / (mt_getrandmax() + 1);
} while (call_user_func($function, $x) < $y);
return (int) floor($x * ($max - $min + 1) + $min);
}
/**
* 'unbiased' creates an unbiased distribution by giving
* each value the same value of one.
*
* @return int
*/
protected static function unbiased()
{
return 1;
}
/**
* 'linearLow' favors lower numbers. The probability decreases
* in a linear fashion.
*
* @return int
*/
protected static function linearLow($x)
{
return 1 - $x;
}
/**
* 'linearHigh' favors higher numbers. The probability increases
* in a linear fashion.
*
* @return int
*/
protected static function linearHigh($x)
{
return $x;
}
}
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