Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!pilchuck!dataio!bright
From: bright@Data-IO.COM (Walter Bright)
Newsgroups: comp.lang.c++
Subject: Re: ambiguity
Keywords: cast, abstract_declarator
Message-ID: <2034@dataio.Data-IO.COM>
Date: 28 Jun 89 20:21:27 GMT
References: <678@rna.UUCP>
Reply-To: bright@dataio.Data-IO.COM (Walter Bright)
Organization: Data I/O Corporation; Redmond, WA
Lines: 15

In article <678@rna.UUCP> kc@rna.UUCP (Kaare Christian) writes:
<Zortech C++ (v1.07) failed to compile the following line,
<    val = min + ( double(y_pointer) / double(slide_ht)) * (max-min);
<It had no problem with the line
<    val = min + ( (double)y_pointer / double(slide_ht)) * (max-min);
<or with the line
<    val = min +   double(y_pointer) / double(slide_ht)  * (max-min);
<Is this an ambiguity in C++, or is Zortech just not smart enough?

Zortech C++ uses 2 token lookahead. That is not enough to distinguish
(double(expression)) from (double)(expression), so the compiler guesses
the latter. Handling all the cases according to Bjarne Stroustrup's rules
requires arbitrary lookahead, which I haven't implemented yet.
The workarounds, though, are in general rather trivial, so this hasn't
been a major problem.