Is there an error in Function?

zzz

I found a great function to convert measurements from centimeters to feet/inches, however when I plug a particular number $cm = 182 I get result of 5' 12" instead of expected 6'.

I can't seem to be able to figure out where the problem is. Here's the function code:

// Cm to ft conversion.
// By Igor Slyusar, http://www.slyusar.com
// Usage: list($feet, $inches) = cmtoft($cm);

function cmtoft() {
  $inches = @func_get_arg(0)*0.3937;
  $feet   = intval($inches/12);
  $inches = round($inches - ($feet*12), 0);
  return array($feet, $inches); 
}

list($feet, $inches) = cmtoft($cm);

halojoy

try to change this line to:

$inches = @func_get_arg(0) / 2.54;

1/2.54 ~ 0.393700787....

While as far as I know
1 in = 2.54 cm ( more often told like: 1 inch = 25.4 mm )
1 ft = 30.48 cm ( 304.8 mm )

Using 0.3937, gives 1 inch ~ 25.4000508.... mm
Which in NOT accurate.

Regards 🙂
halojoy

NogDog

To see why, change this line...

  $inches = round($inches - ($feet*12), 0);

...to this...

  $inches = round($inches - ($feet*12), 6); // <--- change # decimal digits

...and remember that round rounds down or up depending on what the truncated end of the number is.

NogDog

halojoy wrote:
...
Using 0.3937, gives 1 inch ~ 25.4000508.... mm
Which in NOT accurate....

Well, yeah, if you're working in the nano-technology field, perhaps. :rolleyes:

zzz

NogDog wrote:
To see why, change this line...
  $inches = round($inches - ($feet*12), 0);
...to this...
  $inches = round($inches - ($feet*12), 6); // <--- change # decimal digits
...and remember that round rounds down or up depending on what the truncated end of the number is.

Unfortunately this is producing the following result: 5' 11.6534"

Since I'm neither in nano technology nor any other exact science I came up with the following fix:

function cmtoft() {
  $inches = @func_get_arg(0)*0.3937;
  $feet   = intval($inches/12);
  $inches = round($inches - ($feet*12));
  if ($inches == 12) {
  	$feet = $feet + 1;
      $inches = 0;
  }
  return array($feet, $inches); 
}

laserlight

Using func_get_arg(0) seems rather strange here. I would suggest:

function cmtoft($cm) {
    $inches = $cm * 0.3937;
    $feet   = (int)($inches / 12);
    $inches = round($inches - ($feet * 12));
    if ($inches == 12) {
        ++$feet;
        $inches = 0;
    }
    return array($feet, $inches);
}