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[Axiom-developer] Lisp Macros

From: daly
Subject: [Axiom-developer] Lisp Macros
Date: Fri, 23 May 2008 05:33:46 -0500

I'd encourage you to look at 
 "Let Over Lambda -- 50 Years of Lisp"
which is a new book devoted entirely to the subject of macros in lisp.

  "This book is about macros, that is programs that write programs.
   Macros are what make lisp the greatest programming language in
   the world. When used properly, macros enable amazing feats of
   abstraction, programmer productivity, and code efficiency and
   security that are unheard of elsewhere. Macros let you do things
   you simply cannot do in other languages."

Domain-specific languages (DSLs) are trivially easy to create with
macros and vastly simplify programming. The end user can develop
their own notation which can be "processed as written". This enables
the end user to verify that the system is working from their specs.

In my regular work, I have two embedded DSLs within my program which
allows expressing concepts "in the language used by the customer". 
Because they are macros they do not require separate parsers. The 
original Java version had 2 embedded parsers with BNF specifications
as well as a heavyweight XML backend.

In addition, the single macro statements, depending on context, expand
into source program text for an external compiler, a conditional
concurrent assignment statement for logic programming, and an XML
stream for further downstream processes.

Internally within Axiom there are many uses of macros, the most common
one is probably the spadcall macro. If you really want to understand
the internals of Axiom's implementation, you need to understand macros.

If you haven't tried using macros, I'd encourage you to look at this
technology in common lisp.


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