LOGO-L> bug in the 3-d sombrero surface

[MHELHEFNY@FRCU.EUN.EG]

;Helo Everybody
;The code of the true "sombrero" surface which I sent yesterday had
;a bug which causes the grid to draw only in one direction. When you
;run the code with grid = .5 you will not notice it, but for higher
;values it will be noticed; so remove the words:  make "a   on the
;fourth line of the gridz procedure. 
;Last week George Mills found a similar bug in the code of the park
;I agree with him that last minute corrections should be avoided.
;Here is corrected code; excuse me for this fault.
;Best Regards.
;Mhelhefni
;---------------------------------------------------------------
to go
turnon3d cs ;ht
make "step first questionbox [input step bet.(.5  - 2)][]
grid 14 :step
end

to grid :r :step
gridx :r :step gridz :r :step
end

to gridx :r :step
pu
for [x -:r :r :step][for [z -:r :r :step][make "xsq :x* :x make "zsq :z* :z
make "r sqrt(:xsq+ :zsq) +.001
make "f (sin :r*180/pi)/ :r 
setxyz :x*15 :f*200 :z*15] pu setz -zcor pd]
pu 
end

to gridz :r :step
pu
for [z -:r :r :step][for [x -:r :r :step][make "xsq :x* :x make "zsq :z* :z
make "r sqrt(:xsq+ :zsq) +.001
make "f (sin :r*180/pi)/ :r 
setxyz :x*15 :f*200 :z*15] pu setx -xcor pd]
end

to turnon3d
; This is a library procedure for 3-d
perspective
setturtle -1
setxyz 800 1000 800
setturtle 0 
end
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