Re: [Haskell-cafe] nested function application question

[David Menendez]

On Mon, Jan 5, 2009 at 3:16 PM, Brandon S. Allbery KF8NH
 wrote:
> On 2009 Jan 5, at 13:57, David Menendez wrote:
>>
>> 2009/1/5 Ross Mellgren :
>>>
>>> If for some reason you absolutely need to avoid parentheses (mostly as a
>>> thought exercise, I guess), you'd have to have a flipped version of
>>> intercalate:
>>
>> Or a version of ($) that associates differently.
>>
>> infixl 0 $$
>>
>> f $$ x = f x
>>
>> *Main Data.ByteString> :t \x y z -> intercalate $$ intercalate x y $$ z
>> \x y z -> intercalate $$ intercalate x y $$ z :: ByteString
>>-> [ByteString]
>>-> [ByteString]
>>-> ByteString
>
>
> ...at which point we're reinventing Applicative, no?

Is "const" a reinvention of "return"?

You could write the above code with (<*>), but you'd need to convert
back and forth from Identity in order to get the proper Applicative
instance.

runIdentity $ Identity B.intercalate <*> Identity (B.intercalate x
y) <*> Identity z

At that point, you might as well save the noise and write,

B.intercalate (B.intercalate x y) z

-- 
Dave Menendez 

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Re: [Haskell-cafe] nested function application question

[Brandon S. Allbery KF8NH]

On 2009 Jan 5, at 13:57, David Menendez wrote:

2009/1/5 Ross Mellgren :
If for some reason you absolutely need to avoid parentheses (mostly  
as a

thought exercise, I guess), you'd have to have a flipped version of
intercalate:


Or a version of ($) that associates differently.

infixl 0 $$

f $$ x = f x

*Main Data.ByteString> :t \x y z -> intercalate $$ intercalate x y $ 
$ z

\x y z -> intercalate $$ intercalate x y $$ z :: ByteString
-> [ByteString]
-> [ByteString]
-> ByteString



...at which point we're reinventing Applicative, no?

--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com
system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu
electrical and computer engineering, carnegie mellon universityKF8NH


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Re: [Haskell-cafe] nested function application question

[Galchin, Vasili]

Thank you everybody!

Vasili

On Mon, Jan 5, 2009 at 12:57 PM, David Menendez  wrote:

> 2009/1/5 Ross Mellgren :
> > If for some reason you absolutely need to avoid parentheses (mostly as a
> > thought exercise, I guess), you'd have to have a flipped version of
> > intercalate:
>
> Or a version of ($) that associates differently.
>
> infixl 0 $$
>
> f $$ x = f x
>
> *Main Data.ByteString> :t \x y z -> intercalate $$ intercalate x y $$ z
> \x y z -> intercalate $$ intercalate x y $$ z :: ByteString
> -> [ByteString]
> -> [ByteString]
> -> ByteString
>
>
> --
> Dave Menendez 
> >
>
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Re: [Haskell-cafe] nested function application question

[David Menendez]

2009/1/5 Ross Mellgren :
> If for some reason you absolutely need to avoid parentheses (mostly as a
> thought exercise, I guess), you'd have to have a flipped version of
> intercalate:

Or a version of ($) that associates differently.

infixl 0 $$

f $$ x = f x

*Main Data.ByteString> :t \x y z -> intercalate $$ intercalate x y $$ z
\x y z -> intercalate $$ intercalate x y $$ z :: ByteString
 -> [ByteString]
 -> [ByteString]
 -> ByteString


-- 
Dave Menendez 

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Re: [Haskell-cafe] nested function application question

[Ross Mellgren]

In this case you have to use parens -- two dollar signs, like this

B.intercalate $ B.intercalate ByteString [ByteString] $ [ByteString]

would also not type check -- it is exactly equivalent to your first  
example:


B.intercalate (B.intercalate ByteString [ByteString] ([ByteString]))

just with one level of extra parentheses.

If for some reason you absolutely need to avoid parentheses (mostly as  
a thought exercise, I guess), you'd have to have a flipped version of  
intercalate:


flippedIntercalate :: [ByteString] -> ByteString -> ByteString
flippedIntercalate = flip B.intercalate

flippedIntercalate [ByteString] $ B.intercalate ByteString [ByteString]

of course, this is pretty contrived.

-Ross


On Jan 5, 2009, at 1:23 PM, Galchin, Vasili wrote:

yep ... that is exactly what I meant!! so can I use more $'s or must  
I use parens (as you did) to disambiguate?


Vasili

On Mon, Jan 5, 2009 at 12:18 PM, Ross Mellgren hask...@z.odi.ac> wrote:

Did you mean:

B.intercalate (B.intercalate ByteString [ByteString]) [ByteString]

($) applies all the way to the right, so you were giving the inner  
intercalate two lists of ByteString.


-Ross


On Jan 5, 2009, at 1:17 PM, Galchin, Vasili wrote:


Hi Max,

   That is what should happen  The inner B.intercalate will  
produce the ByteString to be used by the B.intercalate.  ??


Vasili

On Mon, Jan 5, 2009 at 12:13 PM, Max Rabkin   
wrote:

2009/1/5 Galchin, Vasili :
> Hello,
>
>   I have the following:
>
> B.intercalate $ B.intercalate
>   ByteString
>   [ByteString]
>   [ByteString]
>
>   I get a type error with this. If I  comment out the 2nd  
B.intercalate

> and the third parameter I get no type errors.

B.intercalate needs a ByteString and a list of ByteStrings. Two
B.intercalates need two ByteStrings and two lists of ByteStrings.

--Max

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Re: [Haskell-cafe] nested function application question

[Galchin, Vasili]

yep ... that is exactly what I meant!! so can I use more $'s or must I use
parens (as you did) to disambiguate?

Vasili

On Mon, Jan 5, 2009 at 12:18 PM, Ross Mellgren  wrote:

> Did you mean:
> B.intercalate (B.intercalate ByteString [ByteString]) [ByteString]
>
> ($) applies all the way to the right, so you were giving the inner
> intercalate two lists of ByteString.
>
> -Ross
>
>
> On Jan 5, 2009, at 1:17 PM, Galchin, Vasili wrote:
>
> Hi Max,
>
>That is what should happen  The inner B.intercalate will produce
> the ByteString to be used by the B.intercalate.  ??
>
> Vasili
>
> On Mon, Jan 5, 2009 at 12:13 PM, Max Rabkin  wrote:
>
>> 2009/1/5 Galchin, Vasili :
>> > Hello,
>> >
>> >   I have the following:
>> >
>> > B.intercalate $ B.intercalate
>> >   ByteString
>> >   [ByteString]
>> >   [ByteString]
>> >
>> >   I get a type error with this. If I  comment out the 2nd
>> B.intercalate
>> > and the third parameter I get no type errors.
>>
>> B.intercalate needs a ByteString and a list of ByteStrings. Two
>> B.intercalates need two ByteStrings and two lists of ByteStrings.
>>
>> --Max
>>
>
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>
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Re: [Haskell-cafe] nested function application question

[Max Rabkin]

On Mon, Jan 5, 2009 at 10:17 AM, Galchin, Vasili  wrote:
> Hi Max,
>
>That is what should happen  The inner B.intercalate will produce
> the ByteString to be used by the B.intercalate.  ??
>
> Vasili
>

Of course. My mistake. Ross Mellgren seems to be on the money though.

--Max
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Re: [Haskell-cafe] nested function application question

[Ross Mellgren]

Did you mean:

B.intercalate (B.intercalate ByteString [ByteString]) [ByteString]

($) applies all the way to the right, so you were giving the inner  
intercalate two lists of ByteString.


-Ross


On Jan 5, 2009, at 1:17 PM, Galchin, Vasili wrote:


Hi Max,

   That is what should happen  The inner B.intercalate will  
produce the ByteString to be used by the B.intercalate.  ??


Vasili

On Mon, Jan 5, 2009 at 12:13 PM, Max Rabkin   
wrote:

2009/1/5 Galchin, Vasili :
> Hello,
>
>   I have the following:
>
> B.intercalate $ B.intercalate
>   ByteString
>   [ByteString]
>   [ByteString]
>
>   I get a type error with this. If I  comment out the 2nd  
B.intercalate

> and the third parameter I get no type errors.

B.intercalate needs a ByteString and a list of ByteStrings. Two
B.intercalates need two ByteStrings and two lists of ByteStrings.

--Max

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Re: [Haskell-cafe] nested function application question

[Galchin, Vasili]

Hi Max,

   That is what should happen  The inner B.intercalate will produce
the ByteString to be used by the B.intercalate.  ??

Vasili

On Mon, Jan 5, 2009 at 12:13 PM, Max Rabkin  wrote:

> 2009/1/5 Galchin, Vasili :
> > Hello,
> >
> >   I have the following:
> >
> > B.intercalate $ B.intercalate
> >   ByteString
> >   [ByteString]
> >   [ByteString]
> >
> >   I get a type error with this. If I  comment out the 2nd
> B.intercalate
> > and the third parameter I get no type errors.
>
> B.intercalate needs a ByteString and a list of ByteStrings. Two
> B.intercalates need two ByteStrings and two lists of ByteStrings.
>
> --Max
>
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Re: [Haskell-cafe] nested function application question

[Max Rabkin]

2009/1/5 Galchin, Vasili :
> Hello,
>
>   I have the following:
>
> B.intercalate $ B.intercalate
>   ByteString
>   [ByteString]
>   [ByteString]
>
>   I get a type error with this. If I  comment out the 2nd B.intercalate
> and the third parameter I get no type errors.

B.intercalate needs a ByteString and a list of ByteStrings. Two
B.intercalates need two ByteStrings and two lists of ByteStrings.

--Max
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