Sections

[E.Ireland@massey.ac.nz]

Original-Via: uk.ac.nsf; Tue, 9 Oct 90 05:04:09 BST
Date: Tue, 9 Oct 90 15:56:59 NZS
From: E.Ireland@massey.ac.nz
To: haskell@cs.glasgow.ac.uk
Subject: Sections
Sender: haskell-request@cs.glasgow.ac.uk

Hi,

A simple question?  Why were sections not included in Haskell?  For
example, I would have liked to be able to write

	(+ 9)		for	(\ x -> x + 9)

	(9 +)		for	(\ x -> 9 + x)

I think I remember seeing sections in an early draft of the Haskell
report, but they do not appear in version 1, so I suppose my question
becomes "why were sections removed"?

I realise that special consideration is required for unary -, however
I think it would be reasonable to state that (- 9) is not a section,
but rather the integer -9, and to state that all other cases to denote
sections.

As a related point, I believe that Hope allows a `?' to be used for
a form of currying, such that for some three argument function f:

	f ? 1 2 	denotes	(\ x -> f x 1 2)

I wouldn't mind `?' being taken for this purpose, since `!' has
already been taken by module Prelude for array indexing, and so I
cannot use the pair of identifiers (`?', '!) for my CSP-like I/O
scheme anyway.

Perhaps these items could be considered for Haskell 2.  Comments please.

				  Evan Ireland (E.Ireland@massey.ac.nz),
School of Information Sciences, Massey University, Palmerston North, NZ.