10.2 Terms and Types

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10.2 Terms and Types

The syntax of types is transcribed directly into an ML datatype from the abstract syntax in Figures 8-1 and 9-1.

   type ty =       TyBool     | TyArr of ty * ty 

The representation of terms is the same as we used for the untyped lambda-calculus (p. 84), just adding a type annotation to the TmAbs clause.

   type term =       TmTrue of info     | TmFalse of info     | TmIf of info * term * term * term     | TmVar of info * int * int     | TmAbs of info * string * ty * term     | TmApp of info * term * term 

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