 VariableExprAST::Codegen = ->
   # Look this variable up in the function.
   V = NamedValues[@name]
-  if V == 0 then throw new Error("Unknown variable name")
+  if not V then throw new Error("Unknown variable name")
 
   # Load the value.
   return Builder.createLoad(V, @name)

  
  # If this is an operator, install it.
  if @Proto.isBinaryOp()
    BinopPrecedence[@Proto.getOperatorName()] = @Proto.getBinaryPrecedence()
  
  # Create a new basic block to start insertion into.
  BB = TheFunction.addBasicBlock("entry")

  isUnaryOp:  -> @isOperator and @args.length == 1
  isBinaryOp: -> @isOperator and @args.length == 2
  getOperatorName: ->
    console.assert(@isUnaryOp() or @isBinaryOp())
    @name

  createArgumentAllocas: (f) ->
