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 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 wrote:

& is already used for this purpose by the Lens library...

On Wed, Oct 9, 2013 at 9:51 PM, Wvv 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

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