Thread

1. scan.l simplifications

   Robert B. Easter <reaster@comptechnews.com> — 2001-01-29T07:36:06Z

   In scan.l, there is:
   
   decimal (({digit}*\.{digit}+)|({digit}+\.{digit}*))
   real 
   ((({digit}*\.{digit}+)|({digit}+\.{digit}*)|({digit}+))([Ee][-+]?{digit}+))
   
   Could this be simplified as:
   
   decimal (({integer}?\.{integer})|({integer}\.{integer}?))
   real ((({decimal})|({integer}))([Ee][-+]?{integer}))
   
   What is the reason if it shouldn't be?  This is just an educational question, 
   I guess. I wouldn't want to waste time writing bad patches. :)  I ran regress 
   with this change and it looked ok.
   
   One reason I can think of right now, is that if the definition of integer or 
   decimal were to change, it might break decimal and real.  Another reason 
   might be a performance loss?
   
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   -------- Robert B. Easter  reaster@comptechnews.com ---------
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2. Re: scan.l simplifications

   Tom Lane <tgl@sss.pgh.pa.us> — 2001-01-29T15:03:40Z

   "Robert B. Easter" <reaster@comptechnews.com> writes:
   > In scan.l, there is:
   > decimal (({digit}*\.{digit}+)|({digit}+\.{digit}*))
   > real 
   > ((({digit}*\.{digit}+)|({digit}+\.{digit}*)|({digit}+))([Ee][-+]?{digit}+))
   
   > Could this be simplified as:
   
   > decimal (({integer}?\.{integer})|({integer}\.{integer}?))
   > real ((({decimal})|({integer}))([Ee][-+]?{integer}))
   
   I think it's better style as it stands.  The latter might be fewer
   characters but it's not easier to understand (IMHO anyway), because
   you have to refer back to more nonterminals to decipher it, and said
   nonterminals have meanings much more complicated than digit.
   
   Also, as you noted, it'd link the definitions of integer/decimal/real
   in ways that might cause trouble later.
   
   			regards, tom lane