This discussion has been interesting: we could really drive this
discussion into the obscure by bringing in 'passing by name' where
actual parameters remain unevaluated until the point of use. :-)
I also agree that Michael's 'post-it-note' analogy is a good one for
novices.
An interesting issue to consider is how to best set up students to
understand pointers in subsequent languages. The 'post-it-note' analogy
seems to be a reasonable starting point. If one understands naming from
that standpoint, transitioning to pointers could be reasonable. I
believe we found that to be the case in our transition to a C++ based
CS2 course, but I haven't examined the data carefully yet.
-rich
[EMAIL PROTECTED]
David MacQuigg wrote:
I agree, there is no reason to dig into call-by-??? terminology with new
"untainted" programmers. The sticky-note analogy is all we need for these
students. The figures in Michael's book are excellent.
However, having been tainted by C, I am finding the discussion interesting. I
just don't understand why there is so much confusion with these call-by terms.
Does the function get a copy of the object or a reference to the original
object? It's got to be one or the other.
At 10:11 PM 5/5/2008 -0500, Michael H.Goldwasser wrote:
Python's model is quite clean, it just doesn't match up perfectly
with the standard call-by-??? terminology.
In call-by-reference evaluation, a function receives an implicit reference to
the argument, rather than a copy of its value.
-- http://en.wikipedia.org/wiki/Call_by_value
By this definition, Python's model is call-by-reference, even though the
reference (pointer) is not seen by the user. C's model is call-by-value, even
though that value can be an explicitly-evaluated address (pointer).
-- Dave
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