Re: LOGO-L> eliminating items randomly from a list

[George Mills <mills@softronix.com>]

It's hard to know if your being to specific and since
Logo is a learning language a good problem to sort out
for themselves (don't give the answer away :-)).

But I think an extract with no randomness makes more sense.
And it would simply be a matter of the user choosing
if the element he/she wishes to extract should be
random or not. Then you'd have a more basic function
younger students are more likely to understand and build on.

This would also simplify the output. There would be
no need to return both what was extracted and what was left.
Becuase they could simply use ITEM with the same argument
they passed to extract to get what will be extracted.
You would not need to remember to use ()'s when you use an
argument and use first and last to extract the answers.

make "alist [1 2 3]

make "aitem 2
show item :aitem :alist
2
show extract :alist :aitem
[1 3]

make "aitem 1 + random count :alist
show item :aitem :alist
3
show extract :alist :aitem
[1 2]

No first's, last's, ()'s or data you don't need or use.

jstclair@omsd.cerf.fred.org wrote:
> 
> Please reply to bh@anarres.CS.Berkeley.EDU (Brian Harvey)  or
> logo-l@gsn.org   NOT   logo-list@gsn.org  or  me.
> 
> -John
> --Message below re-posted by <jstclair@omsd.cerf.fred.org>
> Date - 21 Jan 1998 21:30:24 GMT
> >From - bh@anarres.CS.Berkeley.EDU (Brian Harvey)
> To - jcstclair@omsd
> Subject - Re: LOGO-L> eliminating items randomly from a list
> Usenet: comp.lang.logo
> ------------------
> Post Usenet mail to comp-lang-logo@ucbvax.berkeley.edu
> ------------------
> 
> George Mills <mills@softronix.com> writes:
> >What you want is the index ITEM recieved not the data it pointed at.
> 
> I am beginning to think that what's needed is a new library procedure
> called something like EXTRACT:
> 
> to extract :stuff [:index 1+random count :stuff] [:sofar []]
> if :index = 1 [output list (first :stuff) (se (reverse :sofar) (bf :stuff))]
> output (extract (bf :stuff) (:index-1) (fput first :stuff :sofar))
> end
> 
> Here's how it works:
> 
> ? SHOW (EXTRACT [A B C D A B C D E] 6)
> [B [A B C D A C D E]]
> 
> With only one argument it would pick one at random.  The typical use
> would be to say
> 
> to select
> localmake "result extract :globalvariable
> make "globalvariable last :result
> output first :result
> end
> 
> What do you all think?
> 

-- 
===============================================================
George Mills
email: mills@softronix.com
http://www.softronix.com
The www page contains some very powerful educational software.
Our single most important investment is our kids.

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