Flipped function application

Thu Oct 10 08:46:08 UTC 2013

I believe my previous participation in that discussion was to promote (|>), but at this point I don't really care what it's called, I just think that this operator under any symbolic name should be present in an easily accessible location, preferably in base libs.

I agree with the sentiment!  The OO folk uses this style all the time!   (thing .op1 .op2) meaning op2 (op1 thing).

F# uses (|>).   Maybe (#) is good.    To me (&) looks too commutative because it's usually used for conjunction.

Resolving this kind of no-perfect-solution-but-we-need-a-solution thing is what the core libraries committee is for.  Let's ask them if they'd consider taking it on.

Simon

From: Libraries [mailto:libraries-bounces at haskell.org] On Behalf Of Dan Burton
Sent: 09 October 2013 20:23
To: Edward Kmett
Cc: libraries at haskell.org
Subject: Re: Flipped function application

What were the arguments against (&)? Were they about that choice of symbol in particular, or about the presence of such an operator at all? If the former, then we can keep putting different colors on the bikeshed until we find one everyone likes. If the latter, then I guess we just stick with telling people to import it from lens or diagrams or whatever.

I believe my previous participation in that discussion was to promote (|>), but at this point I don't really care what it's called, I just think that this operator under any symbolic name should be present in an easily accessible location, preferably in base libs.

-- Dan Burton

On Wed, Oct 9, 2013 at 12:00 PM, Edward Kmett <ekmett at gmail.com<mailto:ekmett at gmail.com>> wrote:
Attempting to get (&) added to Data.Function led to a rather profound amount of disagreement last time it was brought up, so eventually we just let the status quo continue.

-Edward

On Oct 9, 2013, at 2:52 PM, Oren Ben-Kiki <haskell-oren at ben-kiki.org<mailto:haskell-oren at ben-kiki.org>> wrote:
& is already used for this purpose by the Lens library...

On Wed, Oct 9, 2013 at 9:51 PM, Wvv <vitea3v at rambler.ru<mailto:vitea3v at rambler.ru>> wrote:
It's looking very strange, that such easy function as flipped function
application is still absent at the base.

x # f = f x
infixl 1 #     -- infix (#) must conflict neither ($), nor (.)

We could add it to Data.Functions and probably to Prelude.

It is very useful function to get rid of parentheses (1); "object looking"
record style (2); left-to-right function reading style (3); nice looking
last argument-data (4)

1) xs # map $ someLong function
   x # some . function . composition
2) car # color
3) myString # lines # map words # concat # filter myFilter # unwords
4) eitherData # either (left long function) (right long function)

Many of possible names are already busy. I made the review of possible
names:

  #    - free; disadvantage: possible conflicts with Magic Hash
  ##  - free; disadvantage: heavy looking; possible conflicts with Magic
Hash
`to`  - free; disadvantage: not easy to read composite functions
 <:    - free;
 &     - free; (conflict with fgl package) disadvantage: looking like
boolean operator
 .:     - free;
 .:.    - free; disadvantage: many dots
 <-|  - free; disadvantage: long name
 <+   - free;
 <~   - free;
 :~    - free;
 -|-   - free; disadvantage: bad looking;
 %    - busy: Data.Ratio
 %%  - free; disadvantage: heavy looking;
  ^    - busy: Prelude
 .^.   - free;
 ^^^ - free; disadvantage: long name
 |.|    - free; disadvantage: strange looking;
  *$    - free; disadvantage: looking like ($)
 <|    - busy: Data.Sequence
 <     - busy: Prelude
 <<   - busy: Text.Html; Text.XHtml.* from html and xhtml package
 <<< - busy: Control.Category
 *     - busy: Prelude
 **   - busy: Prelude
 ***  - busy: Control.Arrow
 <*>  - busy: Control.Applicative
 <**> - busy: Control.Applicative
  !!    - busy: Prelude
  -|   - busy: Control.Parallel.Strategies
 your suggestion  - free;

I prefer (#) , then (.:) and then (<:).

What do you prefer?

Possible looking (copy to your editor to taste them):

2.1 # max 50 # cos # tan # negate # ceiling

2.1 ## max 50 ## cos ## tan ## negate ## ceiling

2.1 `to` max 50 `to` cos `to` tan `to` negate `to` ceiling

2.1 <: max 50 <: cos <: tan <: negate <: ceiling

2.1 & max 50 & cos & tan & negate & ceiling

2.1 .: max 50 .: cos .: tan .: negate .: ceiling

2.1 .:. max 50 .:. cos .:. tan .: negate .:. ceiling

2.1 <-| max 50 <-| cos <-| tan <-| negate <-| ceiling

2.1 <+ max 50 <+ cos <+ tan <+ negate <+ ceiling

2.1 <~ max 50 <~ cos <~ tan <~ negate <~ ceiling

2.1 % max 50 % cos % tan % negate % ceiling

2.1 %% max 50 %% cos %% tan %% negate %% ceiling

2.1 .^. max 50 .^. cos .^. tan .^. negate .^. ceiling

2.1 :~ max 50 :~ cos :~ tan :~ negate :~ ceiling

2.1 |.| max 50 |.| cos |.| tan |.| negate |.| ceiling

2.1 -|- max 50 -|- cos -|- tan -|- negate -|- ceiling

--
View this message in context: http://haskell.1045720.n5.nabble.com/Flipped-function-application-tp5738131.html
Sent from the Haskell - Libraries mailing list archive at Nabble.com<http://Nabble.com>.
_______________________________________________
Libraries mailing list
Libraries at haskell.org<mailto:Libraries at haskell.org>
http://www.haskell.org/mailman/listinfo/libraries

_______________________________________________
Libraries mailing list
Libraries at haskell.org<mailto:Libraries at haskell.org>
http://www.haskell.org/mailman/listinfo/libraries

_______________________________________________
Libraries mailing list
Libraries at haskell.org<mailto:Libraries at haskell.org>
http://www.haskell.org/mailman/listinfo/libraries

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/libraries/attachments/20131010/c504e403/attachment-0001.html>