Display on guile

Display on guile

[for.pdv]

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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)) ())
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))) ())

Why is behaviour of print for a hash different from others?
Am I missing anything?

--regards, Praveen

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Re: Display on guile

[Linas Vepstas]

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)) ())
> 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.

> 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.

--linas

Re: Display on guile

[Praveen D V]

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.
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

Re: Display on guile

[Praveen D V]

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
>

Re: Display on guile

[Linas Vepstas]

2009/3/5 Praveen D V <for.pdv@gmail.com>:

> Hope I'm clear this time.

I hope I am too:

guile> (define x (cons 'c 'd))
guile> x
(c . d)
guile> (define y (cons 'b x))
guile> y
(b c . d)
guile> (define z (cons 'a y))
guile> z
(a b c . d)

--linas

Re: Re: Display on guile

[for.pdv]

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hi,

Oh.. okay. I completely forgot about the printing of immediates vs  
non-immediates.

guile> mh
#(((two 1 2 (a . b))) ((one a . b)))
guile> (define kv (hash-get-handle mh 'one))
guile> kv
(one a . b)
guile> mc
(a . b)
guile> kv
(one a . b)
guile> (set-cdr! kv (cons mc '()))
guile> kv
(one (a . b))
guile> mh
#(((two 1 2 (a . b))) ((one (a . b))))
guile> (pair? kv)
#t
guile> (pair? (cdr kv))
#t
guile> (list? (cdr kv))
#t

I understand it now.

--regards, Praveen

On Mar 5, 2009 11:57pm, Linas Vepstas <linasvepstas@gmail.com> wrote:
> 2009/3/5 Praveen DV for.pdv@gmail.com>:



> > Hope I'm clear this time.



> I hope I am too:



> guile> (define x (cons 'c 'd))

> guile> x

> (c . d)

> guile> (define y (cons 'bx))

> guile> y

> (bc . d)

> guile> (define z (cons 'ay))

> guile> z

> (abc . d)



> --linas


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