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000164_icon-group-sender _Mon Jul 29 15:54:02 1996.msg
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Received: by cheltenham.cs.arizona.edu; Mon, 29 Jul 1996 11:17:01 MST
Message-Id: <31FCD08A.55DC@tees.ac.uk>
Date: Mon, 29 Jul 1996 15:54:02 +0100
From: Hamish Lawson <H.Lawson@tees.ac.uk>
Organization: University of Teesside
X-Mailer: Mozilla 3.0b5aGold (Win95; I)
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To: icon-group@cs.arizona.edu
Subject: Optional expressions
References: <9606221325.AA26435@ursus.cs.arizona.edu> <31D3FA40.1435@tees.ac.uk>
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Status: O
What is the Icon idiom for making one of a series of conjoined
expressions optional? Let's say I have the following series of
expressions
e1 & e2 & e3 & e4
and I want e3 to be evaluated if possible but not to cause the failure
of the enclosing expression. In a string scanning context I've resorted
to
e1 & e2 & e3 | move(0) & e4
but this feels kind of ugly to me.
| Hamish Lawson, School of Computing and Mathematics,
| University of Teesside, Middlesbrough, Cleveland, UK, TS1 3BA
| Tel: +44 1642 212695 Fax: +44 1642 342604
| E-mail: H.Lawson@tees.ac.uk