#
# canola - canon canola 1614p emulator
# Copyright (C) 2011 Peter Miller
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License, version 3, as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <http://www.gnu.org/licenses/>.
#
; ----------  Card-Pocket-Begin  -------------------------------------------
; Title: Cube Root, by P. Miller
; Style: aus
; Disassemble: true
; ----------  Card-Pocket-End  ---------------------------------------------
;
; This subroutine uses the Newton-Raphson method to find the cube root
; of the number in the X register.
;
; x2 = (2 * x1 + a / (x1 * x1)) / 3
;
; a => m14
; x => m13
;
sfj $210
    sm14
    sqrt
    sqrt        ; first approximation is 4th root
    sm13
fj $210
    rm13
    *
    +=
    /
    rm14
    rv
    +=
    rm13
    +=
    rm13
    +=
    /
    3
    +=
    rm13
    rv
    sm13
    -=
    *
    .1
    +=
    mj $210
    sc
    mj $210
    rm13
    srj