Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!uw-beaver!tikal!amc!pilchuck!dataio!bright
From: bright@Data-IO.COM (Walter Bright)
Newsgroups: comp.lang.c
Subject: Re: C sintax
Message-ID: <1471@dataio.Data-IO.COM>
Date: 27 Jan 88 18:35:23 GMT
References: <4083@june.cs.washington.edu>
Reply-To: bright@dataio.UUCP (Walter Bright)
Organization: Data I/O Corporation; Redmond, WA
Lines: 15

In article <4083@june.cs.washington.edu> pardo@uw-june.UUCP (David Keppel) writes:
<<What, precisely, does x+=*a+++*b mean?
<Well, actually it is ambiguous.  There are 2 (or more?) ways to parse
<it.  I'm not sure the behavior is defined from lexer to lexer as to
<which one is preferred.  Here are some possible interpretations:
<    x += *a++ + *b;	/* means add *a to *b and increment a */
<the (an) other is
<    x += *a + ++*b;	/* means increment *b and add that to *a */

It's not ambiguous since the following rule is always applied:
	Tokens are formed from the longest possible sequence of characters
	that could form a token.
Therefore, (x+=*a+++*b) always parses as (x += * a ++ + * b). If there wasn't
this rule, there would be all kinds of problems, as in (x + = * a + ++ * b).
Note that the += was parsed as two separate tokens! Obviously impractical.