patched up array comprehensions somewhat. Parens are still a necessary evil, and there's still probably plenty of edge cases

TODO

@@ -2,6 +2,13 @@ TODO:
 
 * Finish the examples.
 
+* Write a test suite that checks the JS evaluation.
+
+* Figure out a generic way to transform statements into expressions, and
+  use it recursively for returns and assigns on whiles, fors, ifs, etc.
+  
+* If we manage to get array comprehensions working ... object comprehensions?
+
 * Create the documentation page. (amy, idle)
   uv -c . -s coffeescript -t amy --no-lines examples/code.cs > code.html
 

examples/code.cs

@@ -109,9 +109,9 @@ change_a_and_set_b: =>
 b: 20
 
 # Array comprehensions.
-supper: food.capitalize() for food in ['toast', 'cheese', 'wine'].
+supper: [food.capitalize() for food in ['toast', 'cheese', 'wine']]
 
-drink(bottle) for bottle, i in ['soda', 'wine', 'lemonade'] if even(i).
+[drink(bottle) for bottle, i in ['soda', 'wine', 'lemonade'] if even(i)]
 
 # Switch statements ("else" serves as a default).
 switch day

lib/coffee_script/grammar.y

@@ -26,14 +26,14 @@ prechigh
   left     ':'
   right    '-=' '+=' '/=' '*=' '||=' '&&='
   right    DELETE
-  right    RETURN THROW FOR WHILE
+  right    RETURN THROW FOR IN WHILE
   left     UNLESS IF ELSE
   nonassoc "."
 preclow
 
-# We expect 2 shift/reduce errors for optional syntax.
+# We expect 4 shift/reduce errors for optional syntax.
 # There used to be 252 -- greatly improved.
-expect 2
+expect 4
 
 rule
 
@@ -54,12 +54,22 @@ rule
 
   # All types of expressions in our language.
   Expression:
+    PureExpression
+  | Statement
+  ;
+
+  # The parts that are natural JavaScript expressions.
+  PureExpression:
     Literal
   | Value
   | Call
-  | Assign
   | Code
   | Operation
+  ;
+
+  # We have to take extra care to convert these statements into expressions.
+  Statement:
+    Assign
   | If
   | Try
   | Throw
@@ -267,17 +277,17 @@ rule
   # Array comprehensions, including guard and current index.
   For:
   Expression FOR IDENTIFIER
-    IN Expression "."                 { result = ForNode.new(val[0], val[4], val[2]) }
+    IN PureExpression "."             { result = ForNode.new(val[0], val[4], val[2], nil) }
   | Expression FOR
       IDENTIFIER "," IDENTIFIER
-      IN Expression "."               { result = ForNode.new(val[0], val[6], val[2], val[4]) }
+      IN PureExpression "."           { result = ForNode.new(val[0], val[6], val[2], nil, val[4]) }
   | Expression FOR IDENTIFIER
-      IN Expression
-      IF Expression "."               { result = ForNode.new(IfNode.new(val[6], Expressions.new([val[0]])), val[4], val[2]) }
+      IN PureExpression
+      IF Expression "."               { result = ForNode.new(val[0], val[4], val[2], val[6]) }
   | Expression FOR
       IDENTIFIER "," IDENTIFIER
-      IN Expression
-      IF Expression "."               { result = ForNode.new(IfNode.new(val[8], Expressions.new([val[0]])), val[6], val[2], val[4]) }
+      IN PureExpression
+      IF Expression "."               { result = ForNode.new(val[0], val[6], val[2], val[8], val[4]) }
   ;
 
   # Switch/Case blocks.

lib/coffee_script/nodes.rb

@@ -169,9 +169,21 @@ module CoffeeScript
       return !@properties.empty?
     end
 
+    def statement?
+      @literal.is_a?(Node) && @literal.statement? && !properties?
+    end
+
+    def custom_assign?
+      @literal.is_a?(Node) && @literal.custom_assign? && !properties?
+    end
+
+    def custom_return?
+      @literal.is_a?(Node) && @literal.custom_return? && !properties?
+    end
+
     def compile(indent, scope, opts={})
       parts = [@literal, @properties].flatten.map do |v|
-        v.respond_to?(:compile) ? v.compile(indent, scope) : v.to_s
+        v.respond_to?(:compile) ? v.compile(indent, scope, opts) : v.to_s
       end
       @last = parts.last
       parts.join('')
@@ -364,10 +376,10 @@ module CoffeeScript
     custom_return
     custom_assign
 
-    attr_reader :body, :source, :name, :index
+    attr_reader :body, :source, :name, :filter, :index
 
-    def initialize(body, source, name, index=nil)
-      @body, @source, @name, @index = body, source, name, index
+    def initialize(body, source, name, filter, index=nil)
+      @body, @source, @name, @filter, @index = body, source, name, filter, index
     end
 
     def line_ending
@@ -388,18 +400,28 @@ module CoffeeScript
       set_result    = ''
       save_result   = ''
       return_result = ''
+      body = @body
+      suffix = ';'
       if opts[:return] || opts[:assign]
         rvar          = scope.free_variable
         set_result    = "var #{rvar} = [];\n#{indent}"
-        save_result   = "#{rvar}[#{ivar}] = "
+        save_result += "#{rvar}[#{ivar}] = "
         return_result = rvar
         return_result = "#{opts[:assign]} = #{return_result}" if opts[:assign]
         return_result = "return #{return_result}" if opts[:return]
         return_result = "\n#{indent}#{return_result}"
+        if @filter
+          body = CallNode.new(ValueNode.new(LiteralNode.new(rvar), [AccessorNode.new('push')]), [@body])
+          body = @filter ? IfNode.new(@filter, body, nil, :statement) : body
+          save_result = ''
+          suffix = ''
+        end
+      elsif @filter
+        body = IfNode.new(@filter, @body)
       end
 
-      body = @body.compile(indent + TAB, scope)
-      "#{source_part}\n#{indent}#{set_result}for (#{for_part}) {#{var_part}#{index_part}#{indent + TAB}#{save_result}#{body};\n#{indent}}#{return_result}"
+      body = body.compile(indent + TAB, scope)
+      "#{source_part}\n#{indent}#{set_result}for (#{for_part}) {#{var_part}#{index_part}#{indent + TAB}#{save_result}#{body}#{suffix}\n#{indent}}#{return_result}"
     end
   end
 
@@ -444,13 +466,25 @@ module CoffeeScript
     attr_reader :expressions
 
     def initialize(expressions)
-      @expressions = expressions
+      @expressions = expressions.unwrap
+    end
+
+    def statement?
+      @expressions.statement?
+    end
+
+    def custom_assign?
+      @expressions.custom_assign?
+    end
+
+    def custom_return?
+      @expressions.custom_return?
     end
 
     def compile(indent, scope, opts={})
-      compiled = @expressions.unwrap.compile(indent, scope)
+      compiled = @expressions.compile(indent, scope, opts)
       compiled = compiled[0...-1] if compiled[-1..-1] == ';'
-      opts[:no_paren] ? compiled : "(#{compiled})"
+      opts[:no_paren] || statement? ? compiled : "(#{compiled})"
     end
   end
 
@@ -465,7 +499,8 @@ module CoffeeScript
       @condition = condition
       @body      = body && body.unwrap
       @else_body = else_body && else_body.unwrap
-      @condition = OpNode.new("!", @condition) if tag == :invert
+      @tag       = tag
+      @condition = OpNode.new("!", @condition) if @tag == :invert
     end
 
     def <<(else_body)
@@ -495,7 +530,7 @@ module CoffeeScript
     # The IfNode only compiles into a statement if either of the bodies needs
     # to be a statement.
     def statement?
-      @is_statement ||= (@body.statement? || (@else_body && @else_body.statement?))
+      @is_statement ||= ((@tag == :statement) || @body.statement? || (@else_body && @else_body.statement?))
     end
 
     def custom_return?

test/unit/test_parser.rb

@@ -36,7 +36,7 @@ class ParserTest < Test::Unit::TestCase
     assert body.operator == '*'
   end
 
-  def test_lexing_if_statement
+  def test_parsing_if_statement
     the_if = @par.parse("clap_your_hands() if happy").expressions.first
     assert the_if.is_a? IfNode
     assert the_if.condition.literal == 'happy'
@@ -44,6 +44,14 @@ class ParserTest < Test::Unit::TestCase
     assert the_if.body.variable.literal == 'clap_your_hands'
   end
 
+  def test_parsing_array_comprehension
+    nodes = @par.parse("i for x, i in [10, 9, 8, 7, 6, 5] if i % 2 is 0.").expressions
+    assert nodes.first.is_a? ForNode
+    assert nodes.first.body.literal == 'i'
+    assert nodes.first.filter.operator == '==='
+    assert nodes.first.source.literal.objects.last.value == "5"
+  end
+
   def test_parsing
     nodes = @par.parse(File.read('test/fixtures/each.cs'))
     assign = nodes.expressions.first