Re: [Haskell-cafe] Proposal: Non-recursive let

Sure. I have not looked a concrete strictness analyses, but I expect they would treat Conat differently than Integer. In particular,
```
x   does *not* appear strictly in  S x```
```
if S is a lazy constructor.

On 22.07.13 4:54 PM, Edward Kmett wrote:
```
```let x = x +1

is perfectly cromulent when x is sufficiently lazy, e.g. in the one point
compactification of the naturals:

data Conat = S Conat | Z

There it represents infinity with proper sharing.

-Edward

On Jul 22, 2013, at 10:24 AM, Andreas Abel <andreas.a...@ifi.lmu.de> wrote:

```
```On 22.07.2013 10:50, MigMit wrote:
```
```
On Jul 22, 2013, at 12:27 PM, Andreas Abel <andreas.a...@ifi.lmu.de>
wrote:

```
```On 20.07.13 9:36 PM, Evan Laforge wrote:
```
```However, I'm also not agitating for a non-recursive let, I think
that ship has sailed.  Besides, if it were added people would
start wondering about non-recursive where, and it would introduce
an exception to haskell's pretty consistently order-independent
declaration style.
```
```
For functions, recursive-by-default let makes sense.  But for
*values*, intended recursion is rather the exception.  It is useful
for infinite lists and the like.  For values of atomic type like
Int or Bool, recursive let is a bug.
```
```
It seems hard to distinguish between them. What about values that
contain functions, like data T = T Int (Int -> Int)? What about
polymorphic values, that could be functions and could be not?
```
```
I agree.  It cannot be implemented like that.  A thing that could be
implemented is that

let x = e

is an error if x appears strictly in e.  In practice, this could catch some
unintended cases of recursion like

let x = x +1

, but not all of them.

Cheers,
Andreas

--
Andreas Abel  <><      Du bist der geliebte Mensch.

Theoretical Computer Science, University of Munich
Oettingenstr. 67, D-80538 Munich, GERMANY

andreas.a...@ifi.lmu.de
http://www2.tcs.ifi.lmu.de/~abel/

_______________________________________________
```
```
```
```
--
Andreas Abel  <><      Du bist der geliebte Mensch.

Theoretical Computer Science, University of Munich
Oettingenstr. 67, D-80538 Munich, GERMANY

andreas.a...@ifi.lmu.de
http://www2.tcs.ifi.lmu.de/~abel/

_______________________________________________