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1 point by evanrmurphy 2567 days ago | link | parent

> The next thing you might try is mangling variable names.

I think this could work pretty nicely, actually:

  (let x 5         var _x;
    ... )          _x = 5;
                   ...
Here's an example with a global and local variable:

  (= x 6)            var x, _x;
  (let x 5           x = 6;
    (alert x))       
  (alert x)          _x = 5;
                     alert(_x); // => 5

                     alert(x); // => 6
If you use multiple lets with the same variable name in one scope, you would need to differentiate with additional underscores or something:

  (let x 5           var _x, __x;
    (alert x))         
  (let x 6           _x = 5;
    (alert x))       alert(_x); // => 5

                     __x = 6;
                     alert(__x); // => 6
Of course, there is still some risk of variable name collision, and the output isn't super readable. Maybe it's good to have two operators, `let` and `let!`. The former uses function scope, so it's safer and compiles to more readable JavaScript, but it increases the stack size. The latter (let!) is the optimized version that uses one of the schemes we've been talking about.


1 point by rocketnia 2566 days ago | link

What's your policy regarding the ability for people to say (let _x 5 ...) to spoof the mangler? ;) Also, will the name "let!" conflict with ssyntax?

These questions shouldn't keep anyone up nights, but I thought I'd point them out.

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1 point by evanrmurphy 2566 days ago | link

> What's your policy regarding the ability for people to say (let _x 5 ...) to spoof the mangler? ;)

The underscore prefix system would be nice because it's pretty readable, but it's not necessary. In the worst case, we can use gensyms. I thought using underscores for internal variables might work because CoffeeScript does it [1], but maybe it won't. So you raise a good point. :)

> Also, will the name "let!" conflict with ssyntax?

Yes. I'm starting from scratch with the ssyntax. `!` is a regular character now. It can be used in names like `let!`, and when by itself in functional position it compiles to the JavaScript negation operator:

  (! x)   =>   !x
`.`, `:`, `~`, `[]`, `&` and friends are out, too. This may displease my Arc buddies, but I just found it too difficult to think in JavaScript when the gap in meaning between Arc and JS for these characters was so large. `.` compiles to the JS dot operator now, `{}` to the JS object literal and `[]` to the array literal (see [2] for some details). Note that quote ('), quasiquote (`), unquote (,), unquote-splicing (,@) and string quoting (") should all work as expected.

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[1] http://jashkenas.github.com/coffee-script/#comprehensions

[2] http://arclanguage.org/item?id=12948

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