
Hello, All! Does Haskell have some "short-form" for such call: `f (g x) (g x)`, for example: compare (snd x) (snd x) Looks like combinatory logic or `ap` but not exactly... === Best regards, Paul

You can use `liftM2 f g g`
For the example you mentioned, there's also
compare `on` snd
or
comparing snd
with the proper imports (Data.Ord, Data.Function)
On Mon, Dec 4, 2017 at 8:31 AM, Baa
Hello, All!
Does Haskell have some "short-form" for such call: `f (g x) (g x)`, for example:
compare (snd x) (snd x)
Looks like combinatory logic or `ap` but not exactly...
=== Best regards, Paul _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
-- Mihai Maruseac (MM) "If you can't solve a problem, then there's an easier problem you can solve: find it." -- George Polya

Hi!
I think you're looking for Data.Function.on:
http://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Function.html#v:o...
On 04/12/2017, Baa
Hello, All!
Does Haskell have some "short-form" for such call: `f (g x) (g x)`, for example:
compare (snd x) (snd x)
Looks like combinatory logic or `ap` but not exactly...
=== Best regards, Paul _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners

Oh, yes! Exactly, thanks to all!!
Hi!
I think you're looking for Data.Function.on: http://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Function.html#v:o...
On 04/12/2017, Baa
wrote: Hello, All!
Does Haskell have some "short-form" for such call: `f (g x) (g x)`, for example:
compare (snd x) (snd x)
Looks like combinatory logic or `ap` but not exactly...
=== Best regards, Paul _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
_______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners

This led me to look up the definition of on
http://hackage.haskell.org/package/base-4.10.0.0/docs/src/Data.Function.html...
and
discover that punctuation can be used as a variable name for an operator!
On Mon, Dec 4, 2017 at 11:51 AM, Baa
Oh, yes! Exactly, thanks to all!!
Hi!
I think you're looking for Data.Function.on: http://hackage.haskell.org/package/base-4.10.0.0/docs/ Data-Function.html#v:on
On 04/12/2017, Baa
wrote: Hello, All!
Does Haskell have some "short-form" for such call: `f (g x) (g x)`, for example:
compare (snd x) (snd x)
Looks like combinatory logic or `ap` but not exactly...
=== Best regards, Paul _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
_______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
_______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
-- Jeff Brown | Jeffrey Benjamin Brown Website https://msu.edu/~brown202/ | Facebook https://www.facebook.com/mejeff.younotjeff | LinkedIn https://www.linkedin.com/in/jeffreybenjaminbrown(spammy, so I often miss messages here) | Github https://github.com/jeffreybenjaminbrown
participants (4)
-
Baa
-
Dániel Arató
-
Jeffrey Brown
-
Mihai Maruseac