Re: Dangling else

=?ISO-8859-1?Q?Jan_Vorbr=FCggen?= <jvorbrueggen-not@mediasec.de>
5 Mar 2006 02:17:24 -0500

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From: =?ISO-8859-1?Q?Jan_Vorbr=FCggen?= <jvorbrueggen-not@mediasec.de>
Newsgroups: comp.compilers
Date: 5 Mar 2006 02:17:24 -0500
Organization: MediaSec Technologies GmbH
References: 06-02-168 06-02-171
Keywords: parse, syntax

> I haven't used APL much, but troff expressions have the same
> rule--everything left to right, equal precedence--and there I find it
> jarring to read expressions like 1+2*3 as 9.


If a language doesn't have precedence levels, then such expressions
should be disallowed. This is how occam2 does it - you need explicit
parentheses everywhere. A bit of a nuisance, sometimes, that's for
sure - but consistent and, if you take FP expressions into account,
perhaps an improvement from a numerical point of view.


> I think that C makes some bad choices for its precedence levels (and
> assigning left-to-right precedence to what should be nonassociative
> operators) but I still think that precedence levels are useful.
> Mathematicians don't seem to be giving up on them any time soon.


But they have only very few widely accepted precendence levels. The problem
with the C set is that nobody can remember them, let alone remember them
correctly. And a language that doesn't take human cognitive deficits into
account is just badly designed, IMO.


Jan



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