Lisp Style

Some followup from my previous post on Lisp…

— Lisp Resources —

The book "Practical Common Lisp" is available online, published by the author in its entirety.

Also, a CS professor Slava Akhmechet wrote an essay in the same vein, translating from C++ to Lisp — via Xml of all things. 

(In full disclosure, I’ve *never* seen the light of Xml, and verbally abuse it at every opportunity even if only in a hush tone.  It’s like a reflex.  But more people these days are familiar with Xml trees, and the essay is well written).

— Lisp Style —

Also, I’ve noticed I’ve gotten Lisp style wrong slightly.  It is also common to indent to align with the name of the function or language construct being invoked.  This might look like:

   (defun fib (n)
          (if (< n 2)
              1
            (+ (fib (- x 1))
               (fib (- x 2)))))

Note the left paren aligning bellow to the right of ‘defun’, and ‘1’ aligning to the right of ‘if’.  The lesser indent for the ‘+’ operation is used to distinguish the ‘else’ clause for the programmer. 

Don’t align incorrectly:

   ; this code lies!  the programmer incorrectly
   ; aligned 'do-something', which is part of the
   ; addition expresion
   (if (xyz 1 (* 2 3)
       (do-something))
       (something-else))

Instead:

   ; much better.  now it's clear that 'do-something'
   ; is part of the condition expression
   (if (xyz 1
            (* 2 3)
            (do-something))
       (something-else))

There’s even a Lisp plugin for SlickEdit (my code editor of choice) that will automatically adjust the indent for you, as well as add other editor support, and I hear that Emacs has equally great Lisp editing support.