Re: LOGO-L> Numbers or Words?

[tlbelding@htcomp.net (Tony Belding)]

On 25-Jun-97, Olga Tuzova wrote:

>> to happy.test :i
>>    op equalp (sum first :i first bf :i first bf bf :i) ~
>>              (sum last :i last bl :i last bl bl :i)
>> end

>Oh, is it really more natural?

I think it is more natural, based on the way you defined the problem.

>But I'd like my students to know that
>number is a number, not just a word, and it's components (digits)
>have some special qualities. And I want them to introduce to the
>position system of numeration (?) and I'm going to do it with the
>help of Logo.

I'm not sure exactly what you mean by the position system of numeration.

However, I think it's useful to compare the two functions and see why they
give the same results -- and why my function would *not* work with anything
other than base-10 numbers.  :-)

In fact, consider this...  You can divide an integer in Logo by ten this way,
discarding the remainder:

   (print :num [ divided by ten equals ] butlast :num)

In C you can do something similar...

   printf("%d divided by two equals %d\n",num,num>>1);

But why does C divide by two instead of by ten?  It is only because C
considers integers to be base-two numbers instead of base-ten!

Some dialects of Logo can also do that.  This works in Berkeley Logo:

   (print :num [ divided by two equals ] ashift :num -1)

--
   Tony Belding
   http://hamilton.htcomp.net/tbelding/

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