Re: Display on guile

[Praveen D V <for.pdv@gmail.com>]

On Thu, Mar 5, 2009 at 9:38 PM, Praveen D V <for.pdv@gmail.com> wrote:
> hi,
>
> On Thu, Mar 5, 2009 at 8:17 PM, Linas Vepstas <linasvepstas@gmail.com> wrote:
>> 2009/3/5  <for.pdv@gmail.com>:
>>> hi Group,
>>>
>>> I executed these commands..
>>>
>>> $ guile
>>> guile> (define mc (cons 'a 'b))
>>> guile> mc
>>> (a . b)
>>> guile> (define ml (list 1 2 mc))
>>> guile> ml
>>> (1 2 (a . b))
>>> guile> (list mc 1 2 3)
>>> ((a . b) 1 2 3)
>>> guile> (define mh (make-hash-table 2))
>>> guile> (hashq-create-handle! mh 'one mc)
>>> (one a . b)
>>> guile> (hashq-create-handle! mh 'two ml)
>>> (two 1 2 (a . b))
>>> guile> mh
>>> #(((two 1 2 (a . b)) (one a . b)) ())
>
> Small correction, just checked on my cygwin(on windows now), it prints as
> #(((two 1 2 (a . b)) ((one a . b)))
> Also, not sure of the last '()'.  Just a did a cut&paste, something went wrong.
>
>>> guile> (use-modules (ice-9 pretty-print))
>>> guile> (pretty-print mh)
>>> #(((two 1 2 (a . b)) (one a . b)) ())
>>> guile>
>>>
>>> I was expecting handle:'one of hash:mh to be printed in parens as
>>> #(((two 1 2 (a . b)) (one (a . b))) ())
>>
>> According to your logic, you must have also been expecting
>> #(((two (1 2 (a . b))) (one (a . b))) ())
>>
>> which is not what you wrote.
>
> No, not at all.  All I was expecting(assumed), cons always
> prints as "( x . y )".  Notice
> 1. In list it is printed as assumed; either first or last element.
> 2. In hash it prints as assumed; if it is not the first element in value.

Please read it as "In hash it prints as assumed; if it is not the ONLY
member in value."

> If ml2 was created as
> guile> (define ml2 (list mc 1 2))
> guile> ml2
> ((a . b) 1 2)
> and if ml2 was used as value in a hash
> guile> (hashq-create-handle! mh 'one ml2)
> guile>mh
> #(((two 1 2 (a . b)) ((one (a . b) 1 2))))
> Question remains same, why is the behavior different if value is 'cons'?
>
>>> Why is behaviour of print for a hash different from others?
>>> Am I missing anything?
>>
>> When I read the documentation, I see:
>> Return the (key . value) pair for key in the given hash table. If key
>> is not in table then create an entry for it with init as the value,
>> and return that pair.
>>
>> Notice the dot between key and value, which means that
>> hashq-create-handle! behaves like cons, and not like list;
>> from your mail, it seems that you were expecting it to
>> behave like list.
>
> Hope I'm clear this time.
>
> --regards, Paveen
>