From: Andre Nathan <andre@...>
Date: 2004-01-29T22:41:42+09:00
Subject: Bignums and return

Hello

I was doing some testing with two factorial funtions:

def fact1(n)
  if n == 0 
    1
  else
    n * fact1(n-1)
  end
end

with this one, I can go up to fact1(1970) (or fact1(1191) with
'--enable-pthread'). After that, I get a "stack level too deep" error.

The second funtion, below, just adds explicit "return"s:

def fact2(n)
  if n == 0 
    return 1
  else
    return n * fact2(n-1)
  end
end

With this one, I can only go up to fact2(1376) (or up to fact2(841) with
'--enable-pthread'), getting the same error as above after that.

Why does an explicit 'return' or compiling ruby with --enable-pthreads
changes the behaviour?


Also, I'm really puzzled by this one: if I put the two functions on the
*same file*, fact2(1377) (or fact2(842) with '--enable-pthread') will
give the following error: "Bignum can't be coerced into Fixnum" instead
of the "stack level too deep" one.

Why do I get these different errors?

$ ruby -v
ruby 1.8.1 (2003-12-25) [i686-linux]

Best regards,
Andre