Porting D2 code to D1

[Ryan Bloomfield]

Bill Baxter Wrote:
> I think I get your gist.  The syntactic validity requirement is not so 
> much for catching programming errors as it is for keeping parsing simple 
> for tools.  That makes sense, and I think I've actually heard that 
> argument before but just forgot about it.
> 
> I don't like special cases in general, but maybe an exception can be 
> made here.  Version blocks that specify a version of the D language 
> would be treated specially.  That is, the D 1 and 2 specs could be 
> amended to say that any version matching the pattern "D_Version[0-9]+" 
> is special, and the contents of the following block should be ignored by 
> a compiler or tool that does not support that version of the language.
> 
> --bb

That would solve the portability issue with D version standards.  What if a standards compliant compiler adds an additional feature that is syntactically incompatible?  Would a special type of version statement be more useful?  As an example 'dversion(__GNUD__) { ... }', or maybe 'version(D_VERSION,__GNUD__){ ... }'.  

This could even be used to conditionally compile specifically by feature:

version(D_VERSION,__forany__)
{
    forany(...)
        ...
}
else
{
    foreach(...)
        ...
}

just my 2 cents