*       GCD function
        DEFINE('GCD(A,B)')                      :(GCD_END)
GCD     GCD = A
        EQ(B,0)                                 :S(RETURN)
        A = B
        B = REMDR(GCD,B)                        :(GCD)
GCD_END

*       Find first occurrence of element in array
        DEFINE('IDX(ARR,ELM)')                  :(IDX_END)
IDX     IDX = 1
ITEST   EQ(ARR<IDX>,ELM)                        :S(RETURN)
        IDX = IDX + 1                           :(ITEST)
IDX_END

*       Declare array
        SEQ = ARRAY(1200,1)

*       Fill array with Stern-Brocot sequence
        IX = 1
FILL    IX = IX + 1
        SEQ<IX * 2 - 1> = SEQ<IX> + SEQ<IX - 1>
        SEQ<IX * 2> = SEQ<IX>                   :S(FILL)

*       Print first 15 elements
DONE    IX = 1
        S = "First 15 elements:"
P15     S = S " " SEQ<IX>
        IX = IX + 1 LT(IX,15)                   :S(P15)
        OUTPUT = S

*       Print first occurrence of 1..10 and 100
        N = 1
FIRSTN  OUTPUT = "First " N " at " IDX(SEQ,N)
        N = N + 1 LT(N,10)                      :S(FIRSTN)
        OUTPUT = "First 100 at " IDX(SEQ,100)

*       Test GCD between 1000 consecutive members
        IX = 2
GCDTEST EQ(GCD(SEQ<IX - 1>,SEQ<IX>),1)          :F(GCDFAIL)
        IX = IX + 1 LT(IX,1000)                 :S(GCDTEST)
        OUTPUT = "All GCDs are 1."              :(END)
GCDFAIL OUTPUT = "GCD is not 1 at " IX "."

END