Hoi peter, Nadya

>

>create cursor prime ( primenumber i )
>insert into prime value ( 3 )
>
>MaxRange = 100000
>
>t = seconds()
>for i = 5 to MaxRange step 2
>  if IsPrime(i)
>	insert into prime value ( i )
>  endif
>next
>? seconds() - t
>
>func isprime
>	lpar i
>	local n
>	scan
>		n = prime.primenumber
>		if int( i / n ) = i / n
>			return .f.
>		endif
>		if n^2 > i
>			exit
>		endif
>	endscan
>	return .t.
>

What about

CREATE CURSOR Prime (primenumber i)
INSERT INTO Prime VALUES (3)

FOR I = 5 TO 100000 STEP 2
	nSQRT = SQRT(i)
	GO TOP
	LOCATE WHILE prime.primenumber =< nSQRT FOR I % prime.primenumber = 0
	IF !FOUND()
		INSERT INTO Prime VALUES ( i )
	ENDIF
ENDFOR

Long live the fast local data engine !! I wonder if VB can do this as fast as VFP.
So the whole routine Nadya requested can look like the following:

SET TALK OFF
SELECT Numbers
GO BOTTOM
MaxRange = Numbers.Num

** Generate Prime numbers

CREATE CURSOR Prime (primenumber i)
INSERT INTO Prime VALUES (3)

FOR I = 5 TO MaxRange STEP 2
	nSQRT = SQRT(i)
	GO TOP
	LOCATE WHILE prime.primenumber =< nSQRT FOR I % prime.primenumber = 0
	IF !FOUND()
		INSERT INTO Prime VALUES ( i )
	ENDIF
ENDFOR
INDEX ON PrimeNumber TAG Prime

** Determine the missing primenumbers in the gaps in the Numtable

CREATE CURSOR Invert (un I)
SELECT Numbers
GO TOP

nLow = Num
SCAN
	FOR nT = nLow+1 TO Num-1
		IF KEYMATCH(nT,1,"Prime")
			INSERT INTO Invert VALUES (nT)
		ENDIF
	ENDFOR
	nLow=Num
ENDSCAN

Walter,