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Annotation of researchv10no/cmd/sml/src/basics/stamp.sml, revision 1.1.1.1

1.1       root        1: (* Copyright 1989 by AT&T Bell Laboratories *)
                      2: signature STAMP =
                      3: sig
                      4:   type state
                      5:   val new : int * int -> state
                      6:   val current : state -> int * int
                      7:   val move : state * (int * int) -> unit
                      8:   val set : state * int * int -> unit
                      9:   val newTyc : state -> int
                     10:   val newStr : state -> int
                     11:   val newRecord : int -> int
                     12:   val base : int
                     13:   val fixed : int -> bool
                     14:   val bound : int -> bool
                     15:   val global : state
                     16:   val newSig : unit -> int
                     17: end
                     18: 
                     19: structure Stamp : STAMP =
                     20: struct
                     21: 
                     22:   type state = {tycCount : int ref, strCount : int ref}
                     23: 
                     24:   fun new(t: int, s: int) = {tycCount = ref t, strCount = ref s}
                     25: 
                     26:   fun current({tycCount,strCount}: state) = (!tycCount, !strCount)
                     27: 
                     28:   fun set({tycCount,strCount}: state, t: int, s: int) =
                     29:       (tycCount := t; strCount := s)
                     30: 
                     31:   fun move({tycCount,strCount}: state, (t: int, s: int)) =
                     32:       (tycCount := !tycCount + t; strCount := !strCount + s)
                     33: 
                     34:   fun newTyc({tycCount,...}: state) =
                     35:       !tycCount before inc tycCount
                     36: 
                     37:   fun newStr({strCount,...}: state) =
                     38:       !strCount before inc strCount
                     39: 
                     40: 
                     41:   val base = 1000000
                     42: 
                     43:   fun fixed s = s >= base
                     44: 
                     45:   fun bound s = s < base
                     46: 
                     47:   fun newRecord(n:int) = base + (n mod base)
                     48:     (* this allows a slight possibility that two distinct record tycons may
                     49:        be given the same stamp *)
                     50: 
                     51:   val global = new(2*base, 2*base)
                     52: 
                     53: 
                     54:  (* signature stamp generator *)
                     55: 
                     56:   val sigCount = ref(1)
                     57:   fun newSig () = !sigCount before inc sigCount
                     58: 
                     59: end (* structure Stamp *)

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