> It would be useful if the language had the following additions:
>
> 1) "freeze" (and "unfreeze")  varname, ...
>      to freeze a variable's current content, that is to make it
>      constant for the rest of the function (or upto an "unfreeze"
>      within the same function).
>      (volatile variables shall still be changable from other locations).
>
> 2) "hide" (and "unhide") varname, ...
*snip*
> 3) "forget" varname, ...
*snip*
> This would help making programs more robust.

Write smaller functions and your program will be more robust.

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Uenal Mutlu wrote:
> It would be useful if the language had the following additions:
>
> 1) "freeze" (and "unfreeze")  varname, ...
>      to freeze a variable's current content, that is to make it
>      constant for the rest of the function (or upto an "unfreeze"
>      within the same function).
>      (volatile variables shall still be changable from other locations).

Considering that you may have references or pointers to a variable's
contents, making one variable "frozen" may not be enough to make it
immutable:

void foo()
{
  int a = 0;
  int& b = a;
  freeze a;
  // a is now frozen
  b = 1; // OOPS! changed the value of a
}

It is *very* unreasonable to require the compiler to track the
frozen-ness of variables in order to make this example ill-formed. So
instead of making life simple, this keyword is going to introduce an
unnecessary complication without a real usefulness, IMHO. If you want a
variable to be immutable, you should consider making it const in the
first place.

>
> 2) "hide" (and "unhide") varname, ...
>      to make a variable hidden, ie. not accessible for the rest
>      of the current function (or upto an "unhide" within the same
>      function).

Just if name lookup rules weren't already complex enough... ;-)

>
> 3) "forget" varname, ...
>      to forget a variable, ie. to remove it from the list.

What would happen to the variable contents? Will the destructor be
called? If no, then "forget" is the same as "hide", so I don't see why
you're proposing two different keywords. If yes, I see tons of problems
with exception handling. Please remember that you can obtain similar
results in a well-defined manner within current C++ in at least three
different ways:

1) using braces {}
2) using tr1::scoped_ptr (aka boost::scoped_ptr)
3) using boost::optional

>
> This would help making programs more robust.
>

I fail to see how. Could you please provide use-cases supported by code
samples?

Alberto

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