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@@ -85,13 +85,13 @@ For the source:
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 Bus Scheme is currently missing pieces of functionality:
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-=== Bugs
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-* REPL should accept multiline strings
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-
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 === Parser
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-* parse character literals
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-* parse dotted cons cells
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-* Ruby blocks
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+* character literals
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+* multiline strings
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+* escape sequences in strings
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+* string interpolation
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+* dotted cons cells
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+* Ruby blocks?
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 * XML literals?
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 === General

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@@ -8,7 +8,7 @@ if ARGV.empty?
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 elsif ARGV.first == '-e' and ARGV.length == 2
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   puts BusScheme.eval_string(ARGV[1])
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 elsif ARGV.length == 1 and File.exist?(ARGV.first)
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-  puts BusScheme.eval_string "(load \"#{ARGV.first}\")"
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+  puts BusScheme.eval_string("(load \"#{ARGV.first}\")")
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 else
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   puts "Bus Scheme: a scheme interpreter written on the bus.
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 Usage: bus [file | -e \"form\"]

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@@ -20,15 +20,29 @@ module BusScheme
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   VERSION = "0.7.5"
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   PROMPT = '> '
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+  INCOMPLETE_PROMPT = ' ... '
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   LOAD_PATH = ["#{File.dirname(__FILE__)}/scheme/"]
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+  class BusSchemeError < StandardError; end
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+  class ParseError < BusSchemeError; end
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+  class EvalError < BusSchemeError; end
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+  class LoadError < BusSchemeError; end
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+  class IncompleteError < BusSchemeError; end
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+  class ArgumentError < BusSchemeError; end
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+  class AssertionFailed < BusSchemeError; end
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+
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   # Read-Eval-Print-Loop
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   def self.repl
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     loop do
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       puts begin
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              input = Readline.readline(PROMPT)
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              exit if input.nil? # only Ctrl-D produces nil here it seems
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-             BusScheme.eval_string input
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+             begin # allow for multiline input
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+               BusScheme.eval_string input
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+             rescue IncompleteError
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+               input += "\n" + Readline.readline(INCOMPLETE_PROMPT)
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+               retry
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+             end
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            rescue Interrupt
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              'Type "(quit)" or press Ctrl-D to leave Bus Scheme.'
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            rescue BusSchemeError => e

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@@ -21,8 +21,14 @@ module BusScheme
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                end
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       @scope = RecursiveHash.new(locals, @enclosing_scope)
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-      @@stack << self
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-      BusScheme.eval(@body.unshift(:begin.sym)).affect { @@stack.pop }
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+      # we dupe the lambda so that @scope is unique for each call of the function
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+      @@stack << self.dup
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+      
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+      begin
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+        return BusScheme.eval(@body.unshift(:begin.sym))
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+      ensure
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+        @@stack.pop
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+      end
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     end
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     # What's the current scope?
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@@ -47,7 +53,7 @@ module BusScheme
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     end
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     # where were we called from?
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-    def self.trace
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+    def self.stacktrace
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       @@stack.reverse.map { |fn| [fn.symbol, fn.file, fn.line] }
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     end
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   end

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@@ -11,13 +11,13 @@ module BusScheme
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       parse_tokens(tokenize(input).flatten).sexp
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     end
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-    # Turn a list of tokens into a properly-nested S-expression
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+    # Turn a list of tokens into a properly-nested array
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     def parse_tokens(tokens)
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       token = tokens.shift
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       if token == :'('
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         parse_list(tokens)
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       else
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-        raise BusScheme::ParseError unless tokens.empty?
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+        raise ParseError unless tokens.empty?
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         token # atom
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       end
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     end
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@@ -32,7 +32,7 @@ module BusScheme
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             list << element
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           end
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         end
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-        raise ParseError unless element == :')'
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+        raise IncompleteError unless element == :')'
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       end
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     end
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@@ -1,13 +1,6 @@
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 module BusScheme
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   SYMBOL_TABLE = {}
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-  class BusSchemeError < StandardError; end
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-  class ParseError < BusSchemeError; end
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-  class EvalError < BusSchemeError; end
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-  class LoadError < BusSchemeError; end
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-  class ArgumentError < BusSchemeError; end
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-  class AssertionFailed < BusSchemeError; end
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-
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   def self.define(identifier, value)
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     SYMBOL_TABLE[identifier.sym] = value
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   end
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@@ -32,7 +25,8 @@ module BusScheme
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   define 'map', lambda { |fn, list| list.map(lambda { |n| fn.call(n) }).sexp }
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   define 'eval', lambda { |code| eval(code) }
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-
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+  define 'stacktrace', lambda { Lambda.stacktrace }
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+  
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   define 'ruby', lambda { |*code| Kernel.eval code.join('') }
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   define 'send', lambda { |obj, *message| obj.send(*message) }
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@@ -2,7 +2,11 @@ $LOAD_PATH << File.dirname(__FILE__)
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 require 'test_helper'
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 class BusScheme::Lambda
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-  attr_accessor :body, :formals, :environment
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+  attr_accessor :body, :formals, :enclosing_scope
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+
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+  def self.stack
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+    @@stack
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+  end
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 end
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 class BusSchemeLambdaTest < Test::Unit::TestCase
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@@ -67,15 +71,14 @@ class BusSchemeLambdaTest < Test::Unit::TestCase
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   (f (quote b))))"
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   end
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-#   def test_args_work_right
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-#     eval "(define fib (lambda (x)
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-#               (ruby \"p Lambda.scope\")
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-#               (assert (> x 0))
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-# 	      (if (< x 3)
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-# 		  1
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-#                  (+ (fib (- x 1)) (fib (- x 2))))))"
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-#     assert_evals_to 3, "(fib 3)"
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-#   end
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+  def test_nested_function_calls_dont_affect_caller
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+    eval "(define fib (lambda (x)
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+	      (if (< x 3)
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+		  1
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+                 (+ (fib (- x 1)) (fib (- x 2))))))"
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+
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+    assert_evals_to 5, "(fib 5)"
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+  end
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   def test_lambda_rest_args
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     eval "(define rest (lambda args args))"
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@@ -104,4 +107,16 @@ class BusSchemeLambdaTest < Test::Unit::TestCase
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     eval "#{"\n" * 7} (define fab 'warble)"
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     assert_equal 7, Lambda[:fab.sym].line
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   end
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+
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+  def test_stack_gets_popped
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+    # TODO: 
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+  end
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+  
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+  def test_stacktrace
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+    eval "(define gimme-trace (lambda () (stacktrace)))"
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+    eval "(define nest-trace (lambda () (gimme-trace)))"
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+    assert_equal([[:'gimme-trace'.sym, "(eval)", 0],
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+                  [:'nest-trace'.sym, "(eval)", 0]],
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+                 eval("(nest-trace)"))
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+  end
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 end

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@@ -120,8 +120,8 @@ class BusSchemeParserTest < Test::Unit::TestCase
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   end
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   def test_requires_closed_lists
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-    assert_raises(ParseError) { BusScheme.parse "(+ 2 2" }
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-    assert_raises(ParseError) { BusScheme.parse "(+ (* 3 4) 2 2" }
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+    assert_raises(IncompleteError) { BusScheme.parse "(+ 2 2" }
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+    assert_raises(IncompleteError) { BusScheme.parse "(+ (* 3 4) 2 2" }
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   end
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 #   def test_reject_bad_identifiers