From 560bcd4dda60188ddb604c09231c7fccca51e71a Mon Sep 17 00:00:00 2001
From: "Elf M. Sternberg" <elf.sternberg@gmail.com>
Date: Tue, 7 Jul 2015 19:56:11 -0700
Subject: [PATCH] [bug] Fixed the reader to handle dotted lists.

This support is ugly and probably incorrect, but it passes all the current
tests and handles test cases in the original documentation.
---
 chapter1/astAccessors.coffee |  3 ++-
 chapter1/astToList.coffee    |  9 +++++++--
 chapter1/reader.coffee       | 11 +++++++++--
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/chapter1/astAccessors.coffee b/chapter1/astAccessors.coffee
index 413461c..d1e007b 100644
--- a/chapter1/astAccessors.coffee
+++ b/chapter1/astAccessors.coffee
@@ -1,8 +1,9 @@
-{car, cdr} = require 'cons-lists/lists'
+{car, cdr, listp} = require 'cons-lists/lists'
 
 symbol = (form) -> (car form)
 
 module.exports =
+  astObject: (form) -> typeof (car form) == "string"
   aSymbol: symbol
   aValue:  (form) -> (car cdr form)
   isAList: (form) -> (symbol form) == 'list'
diff --git a/chapter1/astToList.coffee b/chapter1/astToList.coffee
index 2a0010e..f9861de 100644
--- a/chapter1/astToList.coffee
+++ b/chapter1/astToList.coffee
@@ -1,7 +1,8 @@
-{car, cdr, cons, listp, nilp, nil, list, listToString} = require 'cons-lists/lists'
-{aSymbol, aValue} = require './astAccessors'
+{car, cdr, cons, listp, nilp, nil, list, pairp, listToString} = require 'cons-lists/lists'
+{aSymbol, aValue, astObject} = require './astAccessors'
 
 # RICH_AST -> LISP_AST
+
 normalizeForm = (form) ->
 
   listToRecord1 = (l) ->
@@ -41,6 +42,10 @@ normalizeForms = (forms) ->
   # Yes, this reifies the expectation than an empty list and 'nil' are
   # the same.
   return nil if nilp forms
+
+  # Handle dotted list.
+  if (astObject forms)
+    return normalizeForm(forms)
   cons(normalizeForm(car forms), normalizeForms(cdr forms))
   
 module.exports =
diff --git a/chapter1/reader.coffee b/chapter1/reader.coffee
index e2b349f..a90a78d 100644
--- a/chapter1/reader.coffee
+++ b/chapter1/reader.coffee
@@ -102,13 +102,20 @@ makeReadPair = (delim, type) ->
       return makeObj(type, nil, line, column)
 
     # IO -> (IO, Node) | Error
+    dotted = false
     readEachPair = (inStream) ->
       [line, column] = inStream.position()
       obj = read inStream, true, null, true
-      if inStream.peek() == delim then return cons obj, nil
+      if inStream.peek() == delim
+        if dotted then return obj
+        return cons obj, nil
       if inStream.done() then return handleError("Unexpected end of input")(line, column)
+      if dotted then return handleError("More than one symbol after dot")
       return obj if (car obj) == 'error'
-      cons obj, readEachPair(inStream)
+      if (car obj) == 'symbol' and (car cdr obj) == '.'
+        dotted = true
+        return readEachPair inStream
+      cons obj, readEachPair inStream
 
     ret = makeObj type, readEachPair(inStream), line, column
     inStream.next()