To improve the readability of Java-based grammars. In my experience,
multiple declarations that do exactly the same thing are distracting and
are a sign of a language that's mired in backward compatibility issues.
Instead of letting users develop different bad habits, why not start fresh
with Java and keep everybody on the same best page?
Well, I had a half-baked idea of making my skeleton compatible with
BYacc/J, but that would require to make the epilogue a big %code instead
of a big %requires, which I don't like.
If the user chooses to put the parser class in a package, it seems useful
to let Bison know the name of it. For example, it's conceivable that
Bison might grow a need to generate additional classes in separate java
files that depend on the parser class. I can't think of exactly what
those classes would be at the moment, but it seems easy to reserve the
possibility. m4 could easily split:
%name-prefix="mypkg.mysubpkg.myclass"
into "mypkg.mysubpkg" and "myclass", right?
Well, yes (one caveat is that a name-prefix of "YY" would create a class
named "YYParser" right now, but that is no big deal).
But if Bison had to create multiple files, it would just copy over the
%code-top and/or %requires to all the files. In fact, I'm already
qualifying all the class names in the skeleton to avoid errors if
somebody imports a "foo.bar.PrintStream" class; it would be no big deal
also to do the same in any other generated class.
All the code in a Java parser resides in a single
Java class or in its inner classes, so it is quite pointless IMO to reserve a
whole package for that.
A whole package? Can't another Java file put classes in the same package?
Yes, of course, you have a point here. But OTOH the same holds if the
package is specified with the Java package keyword in a code block.
Isn't it considered bad practice (poor encapsulation) not to declare a
package?
I'm not suggesting having no package -- but the user should specify it
manually anyway, no matter if in a code block (%{...%}, %code-top,
%requires) or as a %name-prefix. Having one more "mandatory" directive
(%name-prefix to specify the package) in the grammar file makes things
more complex than necessary, IMO.
Paolo
