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List:       haskell-cafe
Subject:    Re: [Haskell-cafe] How to read this syntax?
From:       Robert Dockins <robdockins () fastmail ! fm>
Date:       2005-12-29 16:32:56
Message-ID: 8C3A19AE-93F1-44C3-883B-137E1394604F () fastmail ! fm
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On Dec 29, 2005, at 11:26 AM, David F. Place wrote:

> Hi,
>
> I am trying to read _Arrows, Robots, and Functional Reactive  
> Programming_ by Hudak, et al.
>
> http://www.haskell.org/yampa/AFPLectureNotes.pdf
>
> In section 2.1 there are a number of equations of the form:
>
> g’ :: SF A C
> g’ = arr g
>     = arr f1 >>> arr f2
>
> and
>
> i’ :: SF (A,C) (B,D)
> i’ = arr i
>    = arr (f1 . fst) &&& arr (f2 . snd)
>    = (arr fst >>> arr f1) &&& (arr snd >>> arr f2)
>
> I can't find any reference to the syntax where the function left  
> hand side is just  "space."  I'd greatly appreciate any insight.
>

I'm pretty sure the extra lines are assertions of equality.  That is,  
they are other ways of defining the same function.  That isn't legal  
Haskell syntax as written.

Rob Dockins

Speak softly and drive a Sherman tank.
Laugh hard; it's a long way to the bank.
           -- TMBG




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