Category : Files from Magazines
Archive   : DDJ8702.ZIP
Filename : BASICEX.LST

MODULE Factorial

PUBLIC Last_Fact ! Global variable
PRIVATE Bad_Number ! Local routine
DECLARE DEF Bad_Number ! Function declaration
SHARE Fact_Array(30), Product, MAX ! Local static variables

!------------ Initialize module -----------
let MAX = 30
let Last_Fact = Bad_Number
let Product = Bad_Number
IF MAX > 30 THEN MAT REDIM Fact_Array(MAX) ! Adjust array size
let Fact_Array(1) = 1
FOR I = 2 TO MAX
let Fact_Array(I) = I * Fact_Array(I-1)
NEXT I

!------------ LOCAL ROUTINES --------

DEF Bad_Number = -1.0E+200

!------------ EXPORTED ROUTINES -----

DEF Fact(N)

IF (INT(N) - N) <> 0 THEN
let Fact = Bad_Number
ELSE
let Last_Fact = Product

IF N <= MAX THEN
let Product = Fact_Array(N)
ELSE
let Product = Fact_Array(MAX)
FOR I = MAX+1 TO N
let Product = I * Product
NEXT I

END IF
let Fact = Product
END IF
END DEF

END MODULE