INTERFACE PZSymbol;

(* Small signed integers coded into characters. *)

TYPE
  T = CHAR;
    (*
      Encoding: 'A'..'Z' = +1..+26, 'a'..'z' = -1..-26, '0' = 0. *)

PROCEDURE ToInt(ch: T): INTEGER;
  (*
    The numeric value of "ch". *)
          
PROCEDURE FromInt(i: INTEGER): T;
  (*
    The coded representation of value "i". *)
          
PROCEDURE Complement(ch: T): T;
  (*
    Negates the numeric value of "ch" *)

PROCEDURE DistSqr(a, b: T; complement: BOOLEAN): LONGREAL;
  (*
    A discrepancy measure, squared, between "a" and "b":
    basically, the square of the difference "d = ToInt(a) - ToInt(b)",
    plus a constant term (1/6) to account for
    the quantization error.
    
    If "complement=TRUE", uses "Complement(b(t))" instead of "b"".
  *)
          
PROCEDURE IntgDistSqr(a1, a2, b1, b2: T; complement: BOOLEAN): LONGREAL;
  (*
    The integral of "DistSqr(a(t), b(t), complement)" where "a(t)" 
    interpolates linearly between "a1" and "a2" 
    as "t" goes from 0 to 1; and similarly for "b(t)". *)
          
END PZSymbol.