Rtg To Type Match

Introduction

rtg2typematch is a tool for generating a duck-typing-based strategies that check if an ATerm is of a type as defined in an RTG^?. An example will make this more clear.

Example

Let's take the RTG produced by the example in the manual page of sdf2rtg:

  regular tree grammar
    start Exp
    productions
      Exp      -> Minus(Exp,Exp)
      Exp      -> Plus(Exp,Exp)
      Exp      -> Mod(Exp,Exp)
      Exp      -> Div(Exp,Exp)
      Exp      -> Mul(Exp,Exp)
      Exp      -> Int(IntConst)
      Exp      -> Var(Id)
      IntConst -> <string>
      Id       -> <string>

Apply rtg2typematch:

  > rtg2typematch -i Exp.rtg -o Exp-typematch.str

will result in the module

  module Exp-typematch
  strategies
    is-Exp =
      ?Minus(_, _)
      + ?Plus(_, _)
        + ?Mod(_, _)
          + ?Div(_, _)
            + ?Mul(_, _)
              + ?Int(_)
                + ?Var(_)

    is-IntConst =
      is-string

    is-Id =
      is-string

You can call is-Exp to check whether a term is of sort Exp. Notice that the generated code only looks at the name of the constructor. If the same constructor can be used to produce different sorts, the typematch strategy of all these sort will accept a term that is an application of this constructor.