Re: Combining mutable objects with const references

On Wed, 23 Apr 2008 anonposting@[EMAIL PROTECTED]
 wrote:

> Every time an imperative programmer destructively updates an object,
> he is using an object whose previous values he knows he will not have
> to refer to later.

To be more precise:

The programmer knows that *he* will not refer to the previous value in
the *current* version of the program.

But his destructive update silently claims more than he knows: It
claims that *nobody* will *ever* refer to the previous values, not
even when the program is modified later.

Uniqueness types/monads/... both enable and force the programmer to
state such claims explicitly. IMO this is an example of how a software
engineer reads (or should read) the Curry-Howard isomorphism.

--=20
Matti Nyk=E4nen
professori, Tietojenk=E4sittelytieteen laitos, Kuopion yliopisto
professor, Department of Computer Science, University of Kuopio, Finland