Re: How come Ada isn't more popular?

On Sun, 04 Feb 2007 23:33:40 +0100, Markus E Leypold wrote:

"Dmitry A. Kazakov" <mailbox@xxxxxxxxxxxxxxxxx> writes:

They don't share subtrees they share memory (implementation), which is
casual to the program semantics.

They share representation in the underlying system / VM / whatever you
call it.

Whatever. They are not shared in the sense of aliasing, when you have more
than one name for semantically same thing. 1+1 and 3-1 "share" 2. And this
is irrelevant to where 2 might be allocated or how it were encoded.

When a subtree C of a tree A changes, should it ("it" is an
identity (:-)) in the tree B be changed as well?

Change? There is no "change" in a functional world, only the
production of new values (i.e. new elements from a specific set, in
your case the set of all trees).

(New values? What is the difference between new and old values? Do values
carry RFID chips with timestamps? (:-))

Don't play dumb. There is certainly an order between value occuring in
a (functional) program.

Values "occur"? [ You cannot fix the sentence above, it is semantically
broken. ]

Consider a mapping between nodes of two trees which has to be
preserved. Now a function of the first tree is evaluated, what
happens with the function of the second tree?

g
A ------> B
| |
f| | id = nothing happens
| |
V g V
f(A) ------> B (broken invariant)

The function of the second tree? What are you talking about? Let me
repeat: In pure functional languages nothing "changes".

Consider A = tree, B = its maximal path. When f(A) "occur," [a node is
removed] what happens with B?

Answer: nothing happens, the program is broken. The programmer has to
manually evaluate Max_Path(f(A)). "Maximal path of" is non-functional.

It makes a
difference if you pass an access to a variable instead of passing the
variable as an in/out parameter and there is a difference if you
pass it as an in parameter.

It does because access T and T are different types! T is not passed, access
T is passed (by reference or by value).

You could save much time if you just said that you wanted referential
objects (pointers). Period.

Now my question again, what prevents you from collecting objects accessed
via controlled referential objects?

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
.

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