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3 points by i4cu 2103 days ago | link | parent

This definitely not great, but having to use 'with' is not the real issue for me. In fact if you read through the code you'll notice that this style is often used deliberately (i.e. some people might argue that it's a feature).

I think the bigger issue is that global vars can be used without any errors or conflict warnings. So someone else can create code which sets globals which then gets loaded via libs and will pollute your program. So you could have lib#1 set var 'x' only for it to get clobbered by lib#2's version of var 'x' and arc just ignores this. That's bad. Really bad.



2 points by krapp 2103 days ago | link

>So you could have lib#1 set var 'x' only for it to get clobbered by lib#2's version of var 'x' and arc just ignores this. That's bad. Really bad.

And how often is it intended behavior? How often does one want to have a macro parameter or apparently "local" variable overwrite an existing symbol globally and arbitrarily?

I can see it being useful in the case of "hot patching" code to just redefine a function, but that's still kind of crazy, since now the source code and running code are no longer the same. Might as well just edit the file and reload it, and have one source of truth.

It seems like an anti-feature. Something that seemed like a good idea in theory, but which in practice does more harm than good.

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2 points by akkartik 2102 days ago | link

I'm not following the two of you on precisely what this anti-feature is. Assigning to local variables using '=' does not create new global variables. Can you share a code sample showing what you're talking about?

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1 point by i4cu 2102 days ago | link

> Assigning to local variables using '=' does not create new global variables.

We're referring to the original posts problem where using = inside a function can redefine global variables:

  arc> (= data* '(green red)) 

  arc> (def my-fn () (= data* nil))
  #<procedure: my-fn>
  arc> (my-fn)
  nil
  arc> data*
  nil
Now my comment was referring a bigger problem that falls out of this 'feature' or 'anti-feature' (depending on your point of view).

assume you place this in html.arc

  (= data* '(blue red))

  ; (add-color 'purple)
  (def add-color (color)
    (push color data*))
Then I create apple tracker library 'lib/apples.arc' with:

  (= data* '(green red))

  ; (add-apple 'golden)
  (def add-apple (color)
    (push color data*))
Now at the top level of my progam:

  (load "lib/apples.arc")
  (load "lib/html.arc")
; now say the first apple in storage has gone brown:

  > (string (car data*) " has gone brown")

  "blue has gone brown"
say what? my blue apple has gone brown?

why is there no warning or error on loading my lib? That's pretty bad IMO.

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