Re: Dangling else

henry@spsystems.net (Henry Spencer)
14 Mar 2006 00:48:51 -0500

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[8 earlier articles]
Re: Dangling else henry@spsystems.net (2006-03-05)
Re: Dangling else david.thompson1@worldnet.att.net (Dave Thompson) (2006-03-05)
Re: Dangling else mailbox@dmitry-kazakov.de (Dmitry A. Kazakov) (2006-03-06)
Re: Dangling else rsc@swtch.com (Russ Cox) (2006-03-06)
Re: Dangling else marcov@stack.nl (Marco van de Voort) (2006-03-11)
Re: Dangling else Brian.Inglis@SystematicSW.ab.ca (Brian Inglis) (2006-03-11)
Re: Dangling else henry@spsystems.net (2006-03-14)
Re: Dangling else 148f3wg02@sneakemail.com (Karsten Nyblad) (2006-03-15)
Re: Dangling else DrDiettrich@compuserve.de (Hans-Peter Diettrich) (2006-03-15)
Re: Dangling else marcov@stack.nl (Marco van de Voort) (2006-03-15)
Re: Dangling else henry@spsystems.net (2006-03-16)
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From: henry@spsystems.net (Henry Spencer)
Newsgroups: comp.compilers
Date: 14 Mar 2006 00:48:51 -0500
Organization: SP Systems, Toronto, Canada
References: 06-02-154 06-02-168 06-03-008 06-03-023
Keywords: parse, syntax

Marco van de Voort <marcov@stack.nl> wrote:
>> Bear in mind, though, that attempts to reduce the number of levels have
>> often been found equally unsatisfactory. Pascal tried, and the result was
>> counterintuitive cases where certain parentheses, which everyone agrees
>> ought to be redundant, are in fact necessary.
>
>Could you give examples here? Are you refering to the experimental
>notations for exponentiation 2^(-1) in some dialects ?


No, I'm thinking of things like `(x < y) and (q > 4)', where the
parentheses are mandatory because the Boolean-condition operators
share the precedence levels of the arithmetic operators rather than
having their own.


Wirth himself, in his 1975 Pascal retrospective ("An assessment of the
programming language Pascal", IEEE TransSoftEng 1.2, June 1975), said:
"In retrospect... the decision to break with a widely used tradition seems
ill-advised..."


--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@spsystems.net


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