anchor.diff:                      |> Indent |> braced 
                ]  
   
  +    /// Print all the Grasshopper queries for a model.      
       let printQuery (model: GrassModel) : Doc = 
           Map.toSeq model.Axioms 
           |> Seq.map (fun (name,term) -> printZTermGrass model.SharedVars name term) 
           |> vsep
   
  -    let printGrassError e = 
  -        failwith "not implemented yet" 
  +    /// Print a Grasshopper error. 
  +    let printGrassError e = failwith "not implemented yet" 
   
  +/// Generate a grasshopper model (currently doesn't do anything) 
   let grassModel (i : Backends.Z3.Types.ZModel) : Result<GrassModel,Error>  = 
     ok i 
  
positive.code: 
  [<AutoOpen>] 
  module Types =
      type GrassModel = Backends.Z3.Types.ZModel // Just piggyback on Z3 model for now.  
      type Error = unit 
  
  module Pretty = 
      open Starling.Core.Pretty
  
negative.code:         | Int name -> String name  
          | Bool name -> String name  
          | _ -> failwith "Unimplemented for Grasshopper backend." 
  
      /// Pretty-prints an arithmetic expression.
      let rec printIntExprG (pVar : 'Var -> Doc) : IntExpr<'Var> -> Doc =
  