It works recursively. This will restore your faith in humanity!

I spent far too much time debugging an issue with metacadr (see the
cons-list commits for details), but this now successfully recurses
and all of its code paths are exercised by the factorial/fibonacci
exercises.  This is a Coffeescript implementation of the language
described at the end of chapter 1 of Lisp In Small Pieces.

Also, added a syntax-aware pretty printer.  It's very primitive, but
it's good enough for some debugging.

.gitignore

@@ -3,6 +3,7 @@
 *~
 *.orig
 npm-debug.log
+package.yml
 node_modules/*
 tmp/
 test/

src/lisp_ch1.coffee

@@ -1,6 +1,8 @@
 {listToString, listToVector, pairp, cons, car, cdr, caar, cddr, cdar, cadr, caadr, cadar, caddr, nilp, nil, setcdr, metacadr} = require "cons-lists/lists"
 readline = require "readline"
 {inspect} = require "util"
+print = require "./print"
+
 
 env_init = nil
 env_global = env_init
@@ -55,12 +57,14 @@ extend = (env, variables, values) ->
   else
     if (symbolp variables)
       (cons (cons variables, values), env)
+    else
+      nil
 
 make_function = (variables, body, env) ->
   (values) -> eprogn body, (extend env, variables, values)
 
 invoke = (fn, args) ->
-  fn(args)
+  (fn args)
 
 # Takes a list of nodes and calls evaluate on each one, returning the
 # last one as the value of the total expression.  In this example, we
@@ -71,9 +75,11 @@ eprogn = (exps, env) ->
   if (pairp exps)
     if pairp (cdr exps)
       evaluate (car exps), env
-      return eprogn (cdr exps), env
+      eprogn (cdr exps), env
-    return evaluate (car exps), env
+    else
-  nil
+      evaluate (car exps), env
+  else
+    nil
 
 evlis = (exps, env) ->
   if (pairp exps)
@@ -104,8 +110,6 @@ update = (id, env, value) ->
 # interpreter core.  I can't help but think that this design precludes
 #  pluggable interpreter core.
 
-cadddr = metacadr("cadddr")
-
 astSymbolsToLispSymbols = (node) ->
   return nil if nilp node
   throw "Not a list of variable names" if not (ntype(node) is 'list')
@@ -118,16 +122,18 @@ astSymbolsToLispSymbols = (node) ->
 # Takes an AST node and evaluates it and its contents.  A node may be
 # ("list" (... contents ...)) or ("number" 42) or ("symbol" x), etc.
 
+cadddr = metacadr('cadddr')
+
 evaluate = (e, env) ->
   [type, exp] = [(ntype e), (nvalu e)]
   if type == "symbol"
     return lookup exp, env
-  if type in ["number", "string", "boolean", "vector"]
+  else if type in ["number", "string", "boolean", "vector"]
     return exp
-  if type == "list"
+  else if type == "list"
     head = car exp
     if (ntype head) == 'symbol'
-      return switch (nvalu head)
+      switch (nvalu head)
         when "quote" then cdr exp
         when "if"
           unless (evaluate (cadr exp), env) == the_false_value
@@ -137,9 +143,10 @@ evaluate = (e, env) ->
         when "begin" then eprogn (cdr exp), env
         when "set!" then update (nvalu cadr exp), env, (evaluate (caddr exp), env)
         when "lambda" then make_function (astSymbolsToLispSymbols cadr exp), (cddr exp), env
-        else
+        else invoke (evaluate (car exp), env), (evlis (cdr exp), env)
-          invoke (evaluate (car exp), env), (evlis (cdr exp), env)
+    else
-      return invoke (evaluate (car exp), env), (evlis (cdr exp), env)
+      invoke (evaluate (car exp), env), (evlis (cdr exp), env)
-  throw new Error("Can't handle a #{type}")
+  else
+    throw new Error("Can't handle a #{type}")
 
 module.exports = (c) -> evaluate c, env_global

src/print.coffee

@@ -0,0 +1,21 @@
+{listToString, listToVector, pairp, cons, car, cdr, caar, cddr, cdar, cadr, caadr, cadar, caddr, nilp, nil, setcdr, metacadr} = require "cons-lists/lists"
+
+ntype = (node) -> car node
+nvalu = (node) -> cadr node
+
+evlis = (exps, d) ->
+  if (pairp exps) then evaluate((car exps), d) + " " + evlis((cdr exps), d) else ""
+
+indent = (d) ->
+  ([0..d].map () -> " ").join('')
+    
+evaluate = (e, d = 0) ->
+  [type, exp] = [(ntype e), (nvalu e)]
+  if type == "symbol" then exp
+  else if type in ["number", "boolean"] then exp
+  else if type == "string" then '"' + exp + '"'
+  else if type == "list" then "\n" + indent(d) + "(" + evlis(exp, d + 2) + ")"
+  else throw "Don't recognize a #{type}"
+    
+module.exports = (c) -> evaluate c, 0
+  

src/test_chap1.coffee

@@ -5,5 +5,9 @@ ast = read("(begin (set! fact (lambda (x) (if (eq? x 0) 1 (* x (fact (- x 1)))))
 
 # ast = read("(begin (if (lt 4 2) (+ 4 1)  (+ 2 1)))")
 # ast = read("(begin (set! fact 4) fact)")
-ast = read("(begin ((lambda (t) (if (lt t 2) (+ 4 1)  (+ 2 1))) 4))")
+# ast = read("(begin ((lambda (t) (if (lt t 2) (+ 4 1)  (+ 2 1))) 1))")
+
+# ast = read("(begin (set! fact (lambda (x) (+ x x))) (fact 5))")
+# ast = read("(begin (set! fact (lambda (x) (- x 4))) (fact 5))")
+
 console.log "Result:",  (lisp ast)