Re: GSOC | Extending Common Lisp support

[Jamison Hope <jrh at theptrgroup dot com>]

On Jun 4, 2012, at 9:37 PM, Jamison Hope wrote:

> I just whipped up part of a flet implementation and see the same  
> thing you do
> when running interactively in the REPL or with -f, but I see correct  
> behavior
> when running a file without -f


New data points:


1. I see the same behavior using regular from Scheme and the stock  
Kawa 1.12:

> $ java -cp kawa-1.12.jar kawa.repl
> #|kawa:1|# (define (myfun) 'myfun1)
> #|kawa:2|# (define x myfun)
> #|kawa:3|# (apply x ())
> myfun1
> #|kawa:4|# (myfun)
> myfun1
> #|kawa:5|# (let ((myfun (lambda () 'inner))) (display (myfun))  
> (display (apply myfun ())))
> inner inner
> #|kawa:6|# (myfun)
> inner
> #|kawa:7|# (apply x ())
> inner

Hmm.. what if we shadow the variable and not the function:

> $ java -cp kawa-1.12.jar kawa.repl
> #|kawa:1|# (define (myfun) 'myfun1)
> #|kawa:2|# (define x myfun)
> #|kawa:3|# (apply x ())
> myfun1
> #|kawa:4|# (myfun)
> myfun1
> #|kawa:5|# (let ((x 100)) (display x))
> 100
> #|kawa:6|# x
> #<procedure myfun>
> #|kawa:7|# (x)
> myfun1
> #|kawa:8|# (myfun)
> myfun1
> #|kawa:9|# (let ((x (lambda () 'inner))) (display (x)) (display  
> (apply x ())))
> inner inner
> #|kawa:10|# (myfun)
> inner
> #|kawa:11|# (x)
> inner

That's interesting. The inner binding only clobbers the original if  
it's also a procedure. What if we explicitly declare the top level x's  
type?

> $ java -cp kawa-1.12.jar kawa.repl
> #|kawa:1|# (define (myfun) 'myfun1)
> #|kawa:2|# (define x ::object myfun)
> #|kawa:3|# x
> #<procedure myfun>
> #|kawa:4|# (apply x ())
> myfun1
> #|kawa:5|# (set! x 100)
> #|kawa:6|# x
> 100
> #|kawa:7|# (set! x myfun)
> #|kawa:8|# (apply x ())
> myfun1
> #|kawa:9|# (let ((x 100)) (display x))
> 100
> #|kawa:10|# x
> #<procedure myfun>
> #|kawa:11|# (x)
> myfun1
> #|kawa:12|# (let ((x (lambda () 'inner))) (display (x)))
> inner
> #|kawa:13|# x
> #<procedure myfun>
> #|kawa:14|# (x)
> myfun1

Aha! In that case, things work as we would expect. What if x is  
declared to be a procedure?

> $ rlwrap java -cp kawa-1.12.jar kawa.repl
> #|kawa:1|# (define (myfun) 'myfun1)
> #|kawa:2|# (define x ::procedure myfun)
> #|kawa:3|# myfun
> #<procedure myfun>
> #|kawa:4|# x
> #<procedure myfun>
> #|kawa:5|# (set! x (lambda () 'other))
> #|kawa:6|# x
> #<procedure /dev/stdin:5>
> #|kawa:7|# (myfun)
> myfun1
> #|kawa:8|# (x)
> other
> #|kawa:9|# (set! x myfun)
> #|kawa:10|# x
> #<procedure myfun>
> #|kawa:11|# (x)
> myfun1
> #|kawa:12|# (let ((x (lambda () 'inner))) (display x) (display (x)))
> #<procedure x> inner
> #|kawa:13|# myfun
> #<procedure x>
> #|kawa:14|# (myfun)
> inner

Back through the looking glass. So: what is special about procedure  
bindings?


--
Jamison Hope
The PTR Group
www.theptrgroup.com