On 07-05-2012 13:21, Steven Schveighoffer wrote:
On Fri, 04 May 2012 20:30:05 -0400, Alex Rønne Petersen
<xtzgzo...@gmail.com> wrote:
Purity inference won't happen either way. Purity is part of your API
and also meant to help you reason about your code. If the compiler
just infers purity in a function and you later change the
implementation so it's no longer pure, you break your users' code.
Also, purity would no longer help you reason about your code if it's
not explicit.
It can be pure for the purposes of optimization without affecting code
whatsoever. Inferred purity can be marked separately from explicit
purity, and explicitly pure functions would not be allowed to call
implicitly pure functions.
-Steve
But that kind of inferred purity is something a compiler back end cares
about, not something the language should have to care about at all. In
practice, most compilers *do* analyze all functions for possible
side-effects and use that information where applicable.
(Note that what you described thus is the current situation, just that
inferred purity is not part of the language (no reason it has to be).)
--
- Alex
