PHP中的递归[关闭]

Question

I have a function like this:

function test($T0){
  $T01 = $T0-$T0/2;
  $T02 = $T0+$T0/2;
  if($T01<$T0){
    test($T01);
  } else if($T02<$T0){
    test($T02);
  } else {}
  $result = array($T01,$T02);
    return $result;
  }

  $T0 = 50;
  $result = test($T0);
  echo $result[0];

Why this function is not recursion?

Answer 1

You are missing the return on your recursive calls:

return test($T01);

and

return test($T02);

In addition, you seem to have strange placement of braces on your else clause. Most likely it should be:

else {
    $result = array($T01,$T02);
    return $result;
}

Finally, it's worth noting that this function will (theoretically) cause your code to recurse indefinitely, as you're just dividing a positive number in 2 all the time until it reaches 0. In theory this never happens. In practice, you'll recurse to some very-very small number at which the difference with 0 will be below the floating point precision. In my test this number was 4.9406564584125E-324 (i.e. about 0.0....0494 with ... being 322 zeros).