On 11-12-23 11:34 AM, Patrick Walton wrote:
I do agree that the action-at-a-distance is a potential problem, but experience
suggests that the Standard ML rule leads to the bad outcome less often than the
other alternatives. At this point I've tried all four alternatives
(variable-by-default, tag-by-default, case sensitivity, and the Standard ML
rule) and in my experience the last two avoid mixups far more than the first
two do.
If I'm not mistaken, the Standard ML rule makes it impossible to allow local
variable matching in patterns, because you'd be unable to shadow local
variables and I suspect we probably don't want to go down that road. But I'm
okay with using guards for matching against local variables.
Yeah. One thing that concerns me about that is that it means we lose the
ability to write rebind-the-variable functional-style code:
let x = foo(bleh);
let x = thing(x);
let x = other(x);
...
Personally I find this style ... cute enough, in languages where local
mutation is syntactically clunky, but for us I think it's not super
important to support. We can just re-assign to the same local; it's
terrible form to be changing the type of a variable part way through a
function anyways.
(I'm warming up to the concept of differentiating locally-mutable and
locally-immutable variables using 'mut ...' and 'let ...' though)
-Graydon
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