[MWForum]random numbers, filling

[Daniel Ajoy]

On 8 Feb 2004 at 11:23, Karen Randall wrote:

> Greetings,

Hi Karen,


> Would one of you be kind enough to comment on our class conclusions 
> about a couple small programming problems?  Is there a more elegant 
> way around them?
> 
> 1. The kids want to have random number inputs to setting turtle 
> coordinate locations.  We've been able to do this using setx and sety 
> separately, but not setpos followed by something such as [random 20 
> random 20].  Is this correct?  Can you help us understand why one 
> works but not the other?

That is because [random 20 random 20] is a list with four items: one
word (random), one number (20), one word and one number. 

show first [random 20 random 20]
random

show item 1 [random 20 random 20]
random

show item 2 [random 20 random 20]
20

show item 3 [random 20 random 20]
random

show item 4 [random 20 random 20]
20

What you need is a list of two numbers, like:

show list random 20 random 20
1 17

show list random 20 random 20
3 19

show list random 20 random 20
18 14

"random 20" is a number
"random 20" is a another number
"list" takes both numbers and makes a list with them


> 2.  When trying to fill shapes, we're adding the extra commands to 
> get the turtle inside the shape and off the line it drew getting 
> there so the fill command works, and then sometimes there is still 
> something not cooperating.  Lifting the pen before moving the turtle 
> inside the shape helps a little, but is there an easier way to get 
> solid color shapes (via the turtle and not the graphics tools)?

Here is a general procedure to draw a filled square, 
everything cooperates:

to square :side :color
setc :color
repeat 4 [fd :side rt 90] 
pu rt 45 fd :side fill bk :side rt 45 pd
end


Daniel
OpenWorld Learning