Calling Conventions and Pass By Reference

Randy J. Ray rjray at
Tue Sep 2 20:24:42 BST 2008

>     a=10
>     b=4
>     c=a+b
>     a=20
>     Now what is the value of c?
> For the first example, the answer is pretty clearly 14 but for the 
> second the answer could arguably be either 14 *or* 24.
> I think most programmers are going to go with 14 but I wonder if a 
> totally pass by reference language would cause effects that would mean 
> that you would get used to it being 24. 

Ummm, not unless the value of "c" is actually a representation of the 
expression "a + b" that is dynamically re-interpreted each time you read it. 
Otherwise, even in a reference-only context, "c" was calculated at assignment 
time from the existing values of "a" and "b".

Randy J. Ray                 Silicon Valley Scale Modelers:
rjray at
randy.j.ray at

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