RosettaCodeData/Task/Arithmetic-geometric-mean/QuickBASIC/arithmetic-geometric-mean.basic

PRINT AGM(1, 1 / SQR(2))
END

FUNCTION AGM (a, g)
    DO
        ta = (a + g) / 2
        g = SQR(a * g)
        SWAP a, ta
    LOOP UNTIL a = ta

    AGM = a
END FUNCTION