On Fri, May 1, 2015 at 11:10 AM, Jonathan S. Shapiro <[email protected]> wrote:
> The habit in functional languages has been to use something like "let" as
> the top-level binding form. This grants economy of mechanism, but it leads
> to a design inconsistency.
>
> On the one hand, the bindings in a LET should go out of scope when the let
> does. If so, it should follow that in the following code:
>
> let x = 5
> in
> ...
>
> let x = 3
> in
> ...
>
>
> x is not rebound because it has gone out of scope. Most functional languages
> nonetheless diagnose this as a rebinding.
>
> Does anybody else find this distasteful and confusing?
I don't think i gave an opinion in my last email,
don't really have an F# compiler, but it seems to me that it allows a form of
let x = 5
in ...
let y = x
in ...
I find this particularly nefarious, I could imagine that if this was
usable as some of parallel declarations to a resulting environment
e.g. to avoid the sequential nature of the let forms that allow multiple eq
as in sml's
let val foo = 0;
val bar = foo;
in ... end
the example here: http://fsharpforfunandprofit.com/posts/let-use-do/
let alice = {First="Alice"; Last="Doe"}
let {First=first} = alice
seems to confirm that, and adding the parallel construction it still
suffers from the rebinding problem... seems to have far more in common
with set! than let...
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