Скачать NRand - Normally-Distributed Random Number Generator

15.02.1992
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(*--------------------------------------------------------------*)
(*  NRand --- Return normally-distributed random number         *)
(*--------------------------------------------------------------*)

FUNCTION NRand( Mean : REAL;  StdDev : REAL ) : REAL;

(*--------------------------------------------------------------*)
(*                                                              *)
(* Function:  NRand                                             *)
(*                                                              *)
(* Purpose:   Returns normally distributed random number.       *)
(*                                                              *)
(* Calling sequence:                                            *)
(*                                                              *)
(*    Ran := NRand( Mean : REAL; StdDev : REAL ) : REAL;        *)
(*                                                              *)
(*       Mean   --- Mean of normal distribution                 *)
(*       StdDev --- Standard deviation of normal distribution   *)
(*       Ran    --- Resultant random number                     *)
(*                                                              *)
(* Method:                                                      *)
(*                                                              *)
(*    The Box-Muller transformation is used to get two normal   *)
(*    (0,1)-distributed values. The given mean and standard     *)
(*    deviation are used to scale the results to (Mean, StdDev).*)
(*    The first random number is returned by this call, and the *)
(*    second random number by the next call.                    *)
(*                                                              *)
(*--------------------------------------------------------------*)

(* STATIC VARIABLES *) CONST
   NRand_Available : BOOLEAN = FALSE
                             (* If number already available -- *);
   Saved_NRand     : REAL    = 0.0
                             (* saved from last time through.  *);

VAR
   V1 : REAL;
   V2 : REAL;
   R  : REAL;
   Fac: REAL;

BEGIN (* NRand *)
                      (* Return 2nd random number calculated *)
                      (* last time through here.             *)
   IF NRand_Available THEN