Random Number Generators

RANDOM NUMBER GENERATOR IN RPG IV
The RPG IV program below supports the math bindable API CEERAN0 (Basic 
Random Number Generation). The input parameter C0Seed has a valid 
range of 0 to 2,147,483,646; when the value is 0, the API generates a 
seed from the system's current Greenwich mean time. On return, CEERAN0 
changes the value so it can be used as the new seed in a subsequent 
call.

Output parameter C0RndNbr is a 64-bit double floating-point number 
with a value between 0 and 1. If an invalid seed is used, -1 is 
returned.

The program logic is based on the minimum and maximum values for the 
random number generation. These values are initialized in the D-specs. 
The program uses the %DecH built-in function to convert the floating-
point random number into a packed decimal with a length of 30 digits 
and 29 decimal positions. It then multiplies this value by the maximum 
value: Because 1 is the highest possible random number, the result 
will never be greater than the maximum value. The program's Do loop 
ensures that the random number generation is repeated until the result 
is higher than or equal to the minimum value.

D C0Seed          S              10I 0 Inz(0)
D C0RndNbr        S              8F
 **-- Random Number Conversion:  ---------------------------------- **
D RndNbr          S             10I 0
D MaxNbr          S             10I 0 Inz(9000000)
D MinNbr          S             10I 0 Inz(1000000)
 **
  
**==================================================================**
 **
C                   DoU       RndNbr >= MinNbr
 **
C                   CallB     'CEERAN0'
C                   Parm                    C0Seed
C                   Parm                    C0RndNbr
C                   Parm                    *OMIT
**
C                   Eval      RndNbr = %DecH(C0RndNbr:30:29) * MaxNbr
C                   EndDo
 **
C                   Return


RANDOM NUMBER GENERATOR IN ILE CL (OPM callable)
/*------------------------------------------------------------------*/
/* Generates a random number between 0 and 1.                       */
/* This is a bound ILE CLP program and requires these compile steps */
/* 1. CRTCLMOD                                                      */
/* 2. CRTPGM RANDOM MODULE(RANDOM) SRVPGM(QLEMF)                    */
/*                                                                  */
/* The first parameter is returned as a FLOAT8 (aka FLOAT BIN(53))  */
/* The second is a seed value. After, the SEED value is modified by */
/* this program.                                                    */
/*------------------------------------------------------------------*/
RANDOM: PGM (&RTNVAL &SEED)
DCL &RTNVAL *CHAR (8)
DCL &SEED *CHAR (4)

CALLPRC PRC(CEERAN0) PARM(&SEED &RTNVAL)
ENDPGM

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