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From: Maciej Sobczak <see.my.homepage@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Unary operator after binary operator: legal or not? => Compiler
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Date: Wed, 01 Aug 2007 00:16:41 -0700
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Date: 2007-08-01T00:16:41-07:00
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On 31 Lip, 21:17, Adam Beneschan <a...@irvine.com> wrote:

> What I can't figure out is, my C compiler accepts "c = a+++b"

Yes.

> but it
> doesn't
> seem to accept "c = a+++++b"

Right.

> which should clearly be equivalent to
> c = (a++) + (++b).

Why do you think so? On what basis?

The C (and C++) parser is greedy, which means that it tries to eat as
much as it can to get the valid token. The first two pluses in 'a++++
+b' give a single token '++'. The next two pluses give another *valid*
token, which is again '++'. And so on. The only problem is that two
such tokens one after another, while still being *valid* tokens, do
not form a valid expression (cannot post-increment the r-value that
results from the first post-increment).

Note that you can/should write:

c = a++ + ++b;

which does what you expect (except that post-increment has no benefits
over pre-increment here).

Hint: keep the formatting of your code readable. Your compiler just
refuses the code that would be hard to read by a human being - why do
you consider it to be a bug in the language? :-)

--
Maciej Sobczak
http://www.msobczak.com/