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Comment by cabalamat | Hacker News Reader

AIUI, if I do:

    $x = new Number(-3.2);
    $y = $x->absolute();

Then not only is $y equal to 3.2, $x is now 3.2 as well. Is this correct? If it is, I think it is non-intuitive.

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That is correct. What would you expect it to do?

I would expect $x to remain the same. What's wrong with:

    $x = -3.2;
    $y = abs($x);

Absolutely.

Absolutely non-intuitive?

I think the point here is that you'd have to do something like this

  $x = new Number(1)
  $y = clone $x;
  $y->absolute();

to work with the absolute value of variable $x without actually changing $x

Yes, this is a common source of bugs when you're not sure what is changing. See below, someone suggests to use 'to' and 'as' prefix to convey immutable / mutable methods.

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