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Programming > Compilers > Re: silly quest...
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Re: silly question: prefix vs postfix ops

by Hans Aberg <haberg_20080207@[EMAIL PROTECTED] > Mar 3, 2008 at 10:10 PM

MattR wrote:
> This is more of a language question than a compiler question (and
> therefore should create a religious battle :) ), but I'm wondering if
> the answer has more to do with the compiler. Anyway, why are there
> prefix operators that could just as well be postfix? Why is it !a and
> not a!, or *a and not a* ? I can understand the increment and
> decrement operators, and the & op but expressions like *a[i] would be
> a lot clearer if it were a[i]*, just read the operators from right to
> left. Is it a case of, well, it's always been done this way?

In the Lukasiewicz notation, all operators are prefix.  This is used
in proof theory, for example Shoenfield, "Mathematical Logic". The
postfix notation was invented later - it is particularly easy to
implement with stacks.
   http://en.wikipedia.org/wiki/Polish_notation
   http://en.wikipedia.org/wiki/Reverse_Polish_notation

So today, it is just a notational convention. Mixing in the same
language, may cause ambiguities. This happens for example in music, when
writing chords like A#7. Here, for some reason one may like to write A#
and #7. So some disambiguation is needed if the operator order is to be
kept: parenthesizes, superscripts, or something.

   Hans Aberg




 27 Posts in Topic:
silly question: prefix vs postfix ops
MattR <rosing@[EMAIL P  2008-03-03 10:37:52 
Re: silly question: prefix vs postfix ops
Claudio Saavedra <csaa  2008-03-03 16:24:45 
Re: silly question: prefix vs postfix ops
"Dmitry A. Kazakov&q  2008-03-03 20:42:38 
Re: silly question: prefix vs postfix ops
Alex Colvin <alexc@[EM  2008-03-05 22:02:05 
Re: silly question: prefix vs postfix ops
Hans-Peter Diettrich <  2008-03-06 14:28:53 
Re: silly question: prefix vs postfix ops
glen herrmannsfeldt <g  2008-03-03 12:12:28 
Re: silly question: prefix vs postfix ops
Hans Aberg <haberg_200  2008-03-03 22:10:19 
Re: silly question: prefix vs postfix ops
Marco van de Voort <ma  2008-03-03 22:23:48 
Re: silly question: prefix vs postfix ops
glen herrmannsfeldt <g  2008-03-04 03:06:11 
Re: call by name, was silly question: prefix vs postfix ops
wclodius@[EMAIL PROTECTED  2008-03-04 20:25:54 
Re: call by name, was silly question: prefix vs postfix ops
wclodius@[EMAIL PROTECTED  2008-03-05 20:06:38 
Re: call by name, was silly question: prefix vs postfix ops
anw@[EMAIL PROTECTED] (A  2008-03-07 01:18:09 
Re: call by name, was silly question: prefix vs postfix ops
torbenm@[EMAIL PROTECTED]  2008-03-07 09:32:16 
Re: call by name, was silly question: prefix vs postfix ops
Hans-Peter Diettrich <  2008-03-09 20:16:38 
Re: call by name, was silly question: prefix vs postfix ops
glen herrmannsfeldt <g  2008-03-10 14:39:21 
Re: localized keywords, was call by name
Hans-Peter Diettrich <  2008-03-14 04:27:31 
Re: localized keywords, was call by name
"Dmitry A. Kazakov&q  2008-03-14 18:53:32 
Re: localized languages, was call by name
"Aleksey Demakov&quo  2008-03-14 12:26:59 
Re: localized languages, was call by name
torbenm@[EMAIL PROTECTED]  2008-03-14 09:41:57 
Re: localized languages, was call by name
"Derek M. Jones"  2008-03-15 11:51:55 
Re: localized languages, was call by name
Alex Colvin <alexc@[EM  2008-03-14 22:22:20 
Re: call by name, was silly question: prefix vs postfix ops
Carl Barron <cbarron41  2008-03-10 19:37:16 
Re: algol60 history, was call by name
glen herrmannsfeldt <g  2008-03-14 00:16:14 
Re: call by name, was silly question: prefix vs postfix ops
wclodius@[EMAIL PROTECTED  2008-03-10 19:50:56 
Re: algol, was call by name
Louis Krupp <lkrupp@[E  2008-03-15 17:38:17 
Re: silly question: prefix vs postfix ops
Tony Finch <dot@[EMAIL  2008-03-04 14:20:02 
Re: silly question: prefix vs postfix ops
Ralph Boland <rpboland  2008-03-04 17:59:29 

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