Wait a second, in the JS you've provided don't you have one block nested
inside another? I would have thought that that was the equivalent of
(let [a 123
func (fn [] a)]
(let [a 456]))
Doesn't let in CLJ(S) establish a lexical scope? Also, can you explain what
you mean by symbol-to-value binding? I haven't found very much on the web
about it.
On Wednesday, March 13, 2019 at 10:49:12 PM UTC+5:30, Francis Avila wrote:
>
> Binding to a different variable name in js is how the cljs compiler
> emulates symbol-to-value binding using javascript vars.
>
> It is equivalent to this es6 javascript using let:
>
> {let a = 123, func = function() {return a;}; { let a = 456; }}
>
> On Wednesday, March 13, 2019 at 12:26:15 AM UTC-5, [email protected]
> wrote:
>>
>> When I run the following CLJS code:
>>
>> (let [a 123
>> func (fn [] a)
>> a 456]
>> (func))
>>
>> the block returns 123, which I'm absolutely fine with and have gotten
>> used to since starting programming Clojure(Script).
>>
>> However, in JS if I run the following almost but not quite equivalent
>> code:
>>
>> var a = 123,
>> func = function() {return a;},
>> a = 456;
>>
>> I of course get 456, which is also expected.
>>
>> So it appears, at least on the surface, that when func is created that it
>> evaluates the symbol a at the time of creation, such that func actually
>> becomes (fn [] 123). However, looking at the compiled JS code, what is
>> actually happening is:
>>
>> var a_32455 = (123);
>> var func_32456 = ((function (a_32455) {
>> return (function () {
>> return a_32455;
>> });}) (a_32455) );
>> var a_32457__$1 = (456);
>> func_32456.call(null);
>>
>>
>> which is fascinating, because it isn't actually what I intuitively
>> expected was happening. Instead, it appears as if each instance of the
>> symbol a as a binding in the let binding vector is converted to a different
>> variable in the compiled JS code. So the first a becomes a_32455, and
>> the second becomes a_32457__$1.
>>
>> This isn't actually causing me a problem at all, but I'm really
>> interested to know what exactly is going on, if anyone can explain it. I
>> also wonder if it is something which may trip newcomers from JavaScript and
>> if an explanation should be provided somewhere?
>>
>> Thanks,
>> Ali
>>
>
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