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Re: [Chicken-users] set! on unbound variable

From: Kon Lovett
Subject: Re: [Chicken-users] set! on unbound variable
Date: Fri, 23 Sep 2016 18:45:40 -0700

On Sep 23, 2016, at 6:31 PM, Dan Leslie <address@hidden> wrote:

Sounds like a Chicken Bug,

Chicken calls this a “convenience”. Yes, a std violation but handy using a REPL.

Should be able to defeat.

from the docs[‎0]:

<_expression_> is evaluated, and the resulting value is stored in the location to which <variable> is bound. <Variable> must be bound either in some region enclosing the set! _expression_ or at top level. The result of the set! _expression_ is unspecified.


Sent from my BlackBerry 10 smartphone.
From: Jinsong Liang
Sent: Friday, September 23, 2016 6:27 PM
To: chicken chicken
Subject: [Chicken-users] set! on unbound variable


I have been tripped by the following mistake a few times:

(let ((hello 0))
    (set! helo 1))

I meant to set! on hello. However, due to a typo, I did set! on helo. This bug is extremely hard to debug to me. Is there a way to make Chicken give warning on this? Or how do you handle this issue?

I know probably using set! is not a good programming style. I found that in some situations it is hard to avoid set!.

Thank you!


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