anchor.diff:  module FSharpLex.Compile
   
   open System.Diagnostics
  +open LanguagePrimitives
  +open ExtCore
  +open ExtCore.Collections
   open SpecializedCollections
  -open LanguagePrimitives
   open Graph
   open Regex
   open Ast
  
positive.code:     //
      // OPTIMIZE : Modify this function to use a LazyList to hold the errors
      // instead of an F# list to avoid the list concatenation overhead.
      let rec preprocessMacro pattern cont =
          match pattern with
          | Pattern.Epsilon ->
  
negative.code:             ruleIdentifiers, rules
  
          let compiledRules, compilationErrors =
              rules
              |> Array.mapPartition (fun rule ->
                  compileRule rule options (macroEnv, Set.empty))
  
          // If there are errors, return them; otherwise, create a
          // CompiledSpecification record from the compiled rules.
  