From f6c8e81ea6d8a3c0016b411c3f34fa5d4ea133ba Mon Sep 17 00:00:00 2001
From: Jeremy Ashkenas <jashkenas@gmail.com>
Date: Sat, 16 Jan 2010 23:03:54 -0500
Subject: [PATCH] the existential operator can now be used infix as well

---
 lib/coffee_script/grammar.y                   |  1 +
 lib/coffee_script/nodes.rb                    | 23 +++++++++++++------
 test/fixtures/execution/test_existence.coffee | 20 +++++++++++++++-
 .../fixtures/execution/test_operations.coffee | 10 --------
 4 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/lib/coffee_script/grammar.y b/lib/coffee_script/grammar.y
index 0817762f..1cb1337e 100644
--- a/lib/coffee_script/grammar.y
+++ b/lib/coffee_script/grammar.y
@@ -179,6 +179,7 @@ rule
   | Expression '||' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
   | Expression AND Expression         { result = OpNode.new(val[1], val[0], val[2]) }
   | Expression OR Expression          { result = OpNode.new(val[1], val[0], val[2]) }
+  | Expression '?' Expression         { result = OpNode.new(val[1], val[0], val[2]) }
 
   | Expression '-=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
   | Expression '+=' Expression        { result = OpNode.new(val[1], val[0], val[2]) }
diff --git a/lib/coffee_script/nodes.rb b/lib/coffee_script/nodes.rb
index 84726d74..c446a601 100644
--- a/lib/coffee_script/nodes.rb
+++ b/lib/coffee_script/nodes.rb
@@ -556,7 +556,7 @@ module CoffeeScript
       :not    => '!'
     }
     CHAINABLE        = [:<, :>, :>=, :<=, :===, :'!===']
-    CONDITIONALS     = [:'||=', :'&&=', :'?=']
+    ASSIGNMENT       = [:'||=', :'&&=', :'?=']
     PREFIX_OPERATORS = [:typeof, :delete]
 
     def initialize(operator, first, second=nil, flip=false)
@@ -574,8 +574,9 @@ module CoffeeScript
 
     def compile_node(o)
       return write(compile_chain(o)) if chainable? && @first.unwrap.is_a?(OpNode) && @first.unwrap.chainable?
-      return write(compile_conditional(o)) if CONDITIONALS.include?(@operator.to_sym)
+      return write(compile_assignment(o)) if ASSIGNMENT.include?(@operator.to_sym)
       return write(compile_unary(o)) if unary?
+      return write(compile_existence(o)) if @operator == '?'
       write("#{@first.compile(o)} #{@operator} #{@second.compile(o)}")
     end
 
@@ -588,17 +589,22 @@ module CoffeeScript
         @first.second = ParentheticalNode.new(AssignNode.new(temp, shared))
         shared = temp
       end
-      write("(#{@first.compile(o)}) && (#{shared.compile(o)} #{@operator} #{@second.compile(o)})")
+      "(#{@first.compile(o)}) && (#{shared.compile(o)} #{@operator} #{@second.compile(o)})"
     end
 
-    def compile_conditional(o)
+    def compile_assignment(o)
       first, second = @first.compile(o), @second.compile(o)
       o[:scope].find(first) if @first.unwrap.is_a?(Value)
       sym = @operator[0..1]
-      return "#{first} = (#{first} !== undefined && #{first} !== null) ? #{first} : #{second}" if @operator == '?='
+      return "#{first} = #{ExistenceNode.compile_test(first)} ? #{first} : #{second}" if @operator == '?='
       "#{first} = #{first} #{sym} #{second}"
     end
 
+    def compile_existence(o)
+      first, second = @first.compile(o), @second.compile(o)
+      "#{ExistenceNode.compile_test(first)} ? #{first} : #{second}"
+    end
+
     def compile_unary(o)
       space = PREFIX_OPERATORS.include?(@operator.to_sym) ? ' ' : ''
       parts = [@operator.to_s, space, @first.compile(o)]
@@ -890,13 +896,16 @@ module CoffeeScript
   class ExistenceNode < Node
     children :expression
 
+    def self.compile_test(variable)
+      "(typeof #{variable} !== \"undefined\" && #{variable} !== null)"
+    end
+
     def initialize(expression)
       @expression = expression
     end
 
     def compile_node(o)
-      val = @expression.compile(o)
-      write("(typeof #{val} !== \"undefined\" && #{val} !== null)")
+      write(ExistenceNode.compile_test(@expression.compile(o)))
     end
   end
 
diff --git a/test/fixtures/execution/test_existence.coffee b/test/fixtures/execution/test_existence.coffee
index 47bfbfab..7450b257 100644
--- a/test/fixtures/execution/test_existence.coffee
+++ b/test/fixtures/execution/test_existence.coffee
@@ -2,4 +2,22 @@ print(if my_special_variable? then false else true)
 
 my_special_variable: false
 
-print(if my_special_variable? then true else false)
\ No newline at end of file
+print(if my_special_variable? then true else false)
+
+
+# Existential assignment.
+
+a: 5
+a: null
+a ?= 10
+b ?= 10
+
+print(a is 10 and b is 10)
+
+
+# The existential operator.
+
+z: null
+x: z ? "EX"
+
+print(z is null and x is "EX")
\ No newline at end of file
diff --git a/test/fixtures/execution/test_operations.coffee b/test/fixtures/execution/test_operations.coffee
index 0b996da6..56f57b6c 100644
--- a/test/fixtures/execution/test_operations.coffee
+++ b/test/fixtures/execution/test_operations.coffee
@@ -16,13 +16,3 @@ i: 0
 func: => i++
 
 print(1 > func() < 1)
-
-
-# The conditional assignment based on existence.
-
-a: 5
-a: null
-a ?= 10
-b ?= 10
-
-print(a is 10 and b is 10)
\ No newline at end of file