Spiralling out of control! I should have known better. Merely mentioning the word spiral and suggestions and reminders abound. Below are some spirals done by pupils at a recent Masterclass at the University of Wales . Bangor.

In each case the 'unit' spiral has formed a closed LOOP.

The basic procedure used was:

TO SPIRAL :S :A
IF :S > 40 [STOP]
FD :S  RT :A
SPIRAL :S + 5 :A
END

n.b. this will stop the spiral becoming too large.

You might like to replicate the spirals above by considering suitable values for the variables :S and :A and THEN repeating your procedure several times more!

Or better still you might like to design spirals and loops based on your own ideas!

Or you might like to investigate changes to the size of the angle in ...

TO SPIRAL :S :A
FD :S  RT :A
SPIRAL :S + 1 :A + 5
END

Which may remind some of you about those 'Hallucinations' experienced several years ago ( LOGOland October 2000).

FIRST FORWARD

Beginners can start with FIRST FORWARD 1 to 8 here or go back and follow through the series month by month starting from the Introduction to LOGO in July 1999.

FIRST FORWARD 9

LOPping

Last time you looked at several different sequences of number.

Now consider the following procedure which, unlike those before, uses two variables:

 
TO LOP :X :Y
PR :X
WAIT 120
LOP :Y :X + :Y
END

What do you think is happening this time?

Try 'chasing' through the procedure the values:
x = 1 and y = 1.

No longer surprised!

Why not experiment further changing the value of the fourth line?

For example:

LOP :Y :X + :Y * 2

LOP :Y :X - :Y * 2

LOP :Y :X * 2

Any surprises?

LOP :Y * 2 :X + :Y

Etc.
Etc.
Etc....

1
1
3
5
11
21
43
85
171
341
683
1365
2731
5461
10923
21845
43691
87381
174763
349525
699051
1398101
2796203
5592405
11184811
22369621
44739243
89478485
178956971
357913941
715827883
1431655765
2863311531
5726623061
11453246123
22906492245
45812984491
91625968981
183251937963
366503875925
733007751851
1466015503701
2932031007403
5864062014805
11728124029611
23456248059221
46912496118443
93824992236885
187649984473771
375299968947541
750599937895083
1501199875790165
3002399751580331
Stopped!!! in lop:
lop :y :x * 2 + :y