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From: Dave Angel <davea@davea.name>
Subject: Re: Default mutable parameters in functions
Date: Fri, 4 Apr 2014 22:21:01 -0400 (EDT)
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Xref: csiph.com comp.lang.python:69697

Dennis Lee Bieber <wlfraed@ix.netcom.com> Wrote in message:
> On Fri, 04 Apr 2014 10:00:25 -0400, random832@fastmail.us declaimed the
> following:
> 
>>
>>I can't imagine a language that would work that way. For one, it would
>>also imply that passing a value would change the default for future
>>calls even for non-mutable types.
> 
> 	Some early FORTRAN compilers purportedly had problems with, for
> example:
> 
> 	X = 1
> 	call mutant(1)
> 	Y = 1
> 	
> where
> 
> 	subroutine mutant(y)
> 
> 	y = y + 1
> 	return
> 
> meant that Y now held the value of 2 -- that is, literals were stored in
> mutable memory, and since FORTRAN passes by reference, the address of the
> literal is passed, and the assignment changed the "constant".

I can confirm that,  first hand.

In late 60's, CDC 6400, I deliberately wrote code to exploit that.
  Not for production of course.


-- 
DaveA