public static function shrink(callable $f, $roses)
{
$roses = FP::realize($roses);
if (empty($roses)) {
return self::pure(call_user_func($f));
} else {
return new self(call_user_func_array($f, FP::realize(FP::map(FP::method('getRoot'), $roses))), FP::rgen(FP::map(FP::partial([__CLASS__, 'shrink'], $f), self::remove($roses))));
}
}
function testPartition()
{
$this->assertEquals([[0], [1], [2]], FP::realize(FP::partition(1, FP::range(0, 3))));
$this->assertEquals([[0, 1], [2, 3], [4, 5], [6]], FP::realize(FP::partition(2, FP::range(0, 7))));
$this->assertEquals([[0, 1, 2], [3, 4, 5], [6, 7]], FP::realize(FP::partition(3, FP::range(0, 8))));
}
/**
* creates a generator that produces values from specified generators based on
* likelihoods. The likelihood of a generator being chosen is its likelihood divided
* by the sum of all likelihoods.
*
* Example:
* Gen::frequency(
* 5, Gen::ints(),
* 3, Gen::booleans(),
* 2, Gen::alphaStrings()
* )
*
* @return Generator
*/
public static function frequency()
{
$args = func_get_args();
$argc = count($args);
if ($argc < 2 || $argc % 2 != 0) {
throw new \InvalidArgumentException();
}
$total = array_sum(FP::realize(FP::takeNth(2, $args)));
$pairs = FP::realize(FP::partition(2, $args));
return self::choose(1, $total)->bindGen(function (RoseTree $rose) use($pairs) {
$n = $rose->getRoot();
foreach ($pairs as $pair) {
list($chance, $gen) = $pair;
if ($n <= $chance) {
return $gen;
}
$n = $n - $chance;
}
});
}
public static function enable()
{
FP::env();
}
