Simple Expression Recursion vs Expression/Term/Factor

"Mike Stogden" <stoggers@uniquest.demon.co.uk>
2 Aug 2001 02:46:18 -0400

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Simple Expression Recursion vs Expression/Term/Factor stoggers@uniquest.demon.co.uk (Mike Stogden) (2001-08-02)
Re: Simple Expression Recursion vs Expression/Term/Factor Mark.van.den.Brand@cwi.nl (M.G.J. van den Brand) (2001-08-06)
Re: Simple Expression Recursion vs Expression/Term/Factor kvinay@ip.eth.net (Vinay Kakade) (2001-08-06)
Re: Simple Expression Recursion vs Expression/Term/Factor lucadesantis@infinito.it (luca) (2001-08-06)
Re: Simple Expression Recursion vs Expression/Term/Factor gregod@cs.rpi.edu (Douglas Gregor) (2001-08-06)
Re: Simple Expression Recursion vs Expression/Term/Factor joachim_d@gmx.de (Joachim Durchholz) (2001-08-08)
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From: "Mike Stogden" <stoggers@uniquest.demon.co.uk>
Newsgroups: comp.compilers
Date: 2 Aug 2001 02:46:18 -0400
Organization: Compilers Central
Keywords: syntax
Posted-Date: 02 Aug 2001 02:46:17 EDT

Hi,


Please could someone offer an explanation as to the relative merits of
describing expressions as productions based on two comparable
specifications?


I have seen expressions for the same language described as...


expr -> expr + expr
expr -> expr * expr
etc...


alternatively...


expr -> expr + term
term -> factor | term * factor
factor -> number | identifier
etc...


Just by working through these rules by hand I suspect that they pass the
same language constructs - so what are the relative merits of each approach?


Regards,


Mike Stogden.
[They both define the same language, but the first form has many parses
for any input string while the second defines a unique parse for each
input. -John]




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