Why Java Won't Have Macros

bugbear writes "Carlos Perez has just posted a page that quotes Sun Java 'theologist' Gilad Bracha about why there is no plan to add macros (in the Lisp sense) to Java."

Comments

Re:useless

[reynaert]

No, in Lisp macro's aren't used for inline functions , but for syntax extensions. For a demonstration of what real macros can do, look at The Swine Before Perl. That presentation shows how easy it is to implement special syntax for automatons in Scheme, and how natural & simple the result looks.

Re:OOP

[Dr. Photo]

The macros the article is talking about are Lisp-style macros.

These are not your "shoot self in foot" C macros (i.e. replace text x with text y), but a very powerful and expressive way to have the entire language at your disposal at compile time.

If you've seen the neat tricks you can do with C++ templates (template metaprogramming, etc), you might have an idea of what real macros would be like, when severely watered-down.

Lisp macros make things like Generic programming and OOP very simple to add to a language, as well as almost any other conceivable programming construct.

For instance, with proper macros in Java, you wouldn't ask, "When will templates be added to Java?"; you could add them yourself.

If this is what Jabba does, then Jabba will lose.

[ArmorFiend]

The crux of his argument is that user defined macros make code unreadable. If users are able to create their own macro constructs, they'll be "making their programs unreadable for everyone else". This is pure hogwash from someone that's probably never used hairy-chested lisp macros seriously. I'll demonstrate to you the hogwashishness in two phases.

Flash-back to 1969 when the same arguments were put forward by assembly programmers against named functions:

User defined functions make code unreadable. If users are able to create their own functions, they'll be "making their programs unreadable for everyone else".

History has show that user defined functions are good. People are finally realizing that lisp macros are perhaps an equally important good. By taking this position, Jabba is positioning itself on the losing side of history.

Seriously, what's easier to read:

// macro-less call
{
window.context().glxMakeContextCurrent();
float[4] color = window.fgColor();
glColor(color);
glPushMatrix() ;
glIdent();
glAlphaBlend( GL_FALSE );
...non-boiler-plate-code...
glAlphaBlend( GL_TRUE );
glPopMatrix();
}

OR

// macro call
withGLDrawing (color) {
...non-boiler-plate-code...
}

If you look at it in terms of lines of code, in terms of error-prone-ness, in terms of high-level versus low-level, in terms of maintainability, ONLY AN IDIOT WOULD CHOOSE AGAINST MACROS.

Okay, sorry for being ornery, but mod this scruffy post up!