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Newsgroups: comp.lang.forth
Subject: Re: lisp can sum a list of numbers with 2 parens and a +, can forth useloop to make something similar?
Date: Wed, 11 Feb 2015 09:19:16 +0000 (UTC)
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On Mon, 09 Feb 2015 08:00:02 -0500, Doug Hoffman wrote:

> On 2/9/15 3:55 AM, WJ wrote:
> 
>> Calculate the average of the numbers in a list, traversing it only once
>> and making no assignments to a variable:
>>
>> Gauche Scheme:
>>
>> (define (average numbers)
>>    (apply /
>>      (fold (lambda (x accum) (map + (list x 1) accum))
>>            '(0 0)
>>            numbers)))
>>
>> (define numbers `(,@(iota 9 -9 2) 633 ,@(iota 9 22))) numbers
>>   ===>
>> (-9 -7 -5 -3 -1 1 3 5 7 633 22 23 24 25 26 27 28 29 30)
>>
>> (average numbers)
>>   ===>
>> 858/19
>>
>> (inexact (average numbers))
>>   ===>
>> 45.1578947368421
>>
>>
>> The easy way would be
>>
>> (/. (apply + numbers) (length numbers))
>>   ===>
>> 45.1578947368421
>>
>> but that traverses the list twice: once to add up the numbers and once
>> to determine the length of the list.
> 
> 
> : ave{ 0e 0
>    begin parse-name 2dup s" }" compare
>    while >float drop f+ 1+
>    repeat 2drop s>f f/ f. ;
> 
> ave{ -9 -7 -5 -3 -1 1 3 5 7 633 22 23 24 25 26 27 28 29 30 }
> 45.1578947368421 ok
> 
> \ the easier way would be to use library code: f{ -9 -7 -5 -3 -1 1 3 5 7
> 633 22 23 24 25 26 27 28 29 30 } average: f. 45.1578947368421 ok

Computing is no longer 'about computors' it's about human cognition:
saving effort. Yes, minimal text is part of saving-effort.
But recognise & select [ie. menu] instead of 'coding' is cheaper.
Also color economically adds cognitive power.
Where's the VISUAL forth?