context-free grammar

[uri]

Jonathan M Davis Wrote:

> On Friday 04 March 2011 17:05:57 Simon Buerger wrote:
> > It is often said that D's grammar is easier to parse than C++, i.e. it
> > should be possible to seperate syntactic and semantic analysis, which
> > is not possible in C++ with the template-"< >" and so on. But I found
> > following example:
> > 
> > The Line "a * b = c;" can be interpreted in two ways:
> > -> Declaration of variable b of type a*
> > -> (a*b) is itself a lvalue which is assigned to.
> > 
> > Current D (gdc 2.051) interprets it always in the first way and yields
> > an error if the second is meant. The Workaround is simply to use
> > parens like "(a*b)=c", so it's not a real issue. But at the same time,
> > C++ (gcc 4.5) has no problem to distinguish it even without parens.
> > 
> > So, is the advertising as "context-free grammar" wrong?
> 
> Umm. How could a * b be assigned to? It's definitely not an lvalue. Do you mean 
> that an overloaded opBinary!"*" is used which returns a ref? It certainly can't 
> be done normally.

Explain why (a*b) is lvalue in bearophile's second example. This is one of the weird things in D. The language is too complex. It takes years to find out about the corner cases. I wouldn't use it for anything reliable