function f_reduce($combiner, $in, $identity=null) {
//adds the first item with the rest, then does the same with the rest.
if(!empty($in)) {
return $combiner(
f_first($in),
f_reduce(
$combiner,
f_rest($in),
$identity
)
);
} else {
return $identity;
}
}
function f_flatten($in) {
return f_reduce(
function($a, $b) {
if(is_array($a)) {
$a = f_flatten($a);
}
return array_merge((array)$a, (array)$b);
},
$in
);
}
