Composition operator [was: Re: Records in Haskell]

Isaac Dupree ml at
Thu Jan 12 19:20:41 CET 2012

On 01/12/2012 07:06 AM, Matthew Farkas-Dyck wrote:
> On 09/01/2012, Greg Weber <greg at> wrote:
>> Note that a move to a different operator for function composition
>> (discussed in dot operator section) would make things easier to parse:
>>     b<~ .a
>> where the unicode dot might be even nicer.
> I told you so (^_^)
> Unicode dot (∘) would be optimal, since that's what it's for. If to
> type '∘' is awkward, then one can use (Control.Category.<<<). We need
> not (and, in my opinion, should not) define another operator.

Is ∘ (U+2218 RING OPERATOR)* in Prelude yet? We should propose that.**

I checked my compose-key (Linux)
and it can produce middle-dot · (U+00B7 MIDDLE DOT) with "Compose . -", 
but not ∘ in any way***.  If we use the proper Unicode operator ∘, then 
let's make a wiki page for all the common OSes/input methods, saying how 
to input it (aside from copy/paste).  Is there anything on the Web 
somewhere already?  Did Perl do this ( - I think they introduced some 
Unicode-based syntax)?  There's , which has some 
information (none of which let me write ∘ in an e-mail without using 

* found out using
** "(negate ∘ (+ 1)) 3" doesn't work in my ghci 7.0.3 with no 
command-line options (and a UTF-8 system locale and UTF-8-compatible 
terminal, as is typical these days).
*** I checked the list in /usr/share/X11/locale/en_US.UTF-8/Compose

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