Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.forth > #20156 > unrolled thread

Filtering

Back to article view | Back to comp.lang.forth

Contents

  Filtering "WJ" <w_a_x_man@yahoo.com> - 2013-03-02 07:48 +0000
    Re: Filtering mhx@iae.nl (Marcel Hendrix) - 2013-03-02 11:17 +0200
    Re: Filtering "Charles Childers" <crc@retroforth.org> - 2013-03-02 11:18 -0500
      Re: Filtering "A. K." <akk@nospam.org> - 2013-03-02 17:55 +0100
        Re: Filtering Marc Olschok <nobody@nowhere.invalid> - 2013-03-03 22:11 +0000

#20156 — Filtering

Given a sequence of numbers, keep those that are odd and
multiply them by 100.

Factor:


USE: sequences.extras

{ 1 1 2 3 5 8 13 21 } [ odd? ] [ 100 * ] filter-map
{ 100 100 300 500 1300 2100 }

[toc] | [next] | [standalone]

#20163

"WJ" <w_a_x_man@yahoo.com> writes Re: Filtering

> Given a sequence of numbers, keep those that are odd and
> multiply them by 100.

> Factor:


> USE: sequences.extras

> { 1 1 2 3 5 8 13 21 } [ odd? ] [ 100 * ] filter-map
> { 100 100 300 500 1300 2100 }


8 integer array x{   1 1 2 3 5 8 13 21 x{ #=>  
: fm ( x -- ) dup cdim 0 ?do dup i } @ dup 1 and if 100 * . else drop endif loop drop ;

x{ fm 100 100 300 500 1300 2100  ok

Or:

: fm  BEGIN  bl word dup C@  
      WHILE  count evaluate  dup 1 and IF 100 * . ELSE drop ENDIF 
      REPEAT drop ;
      
FORTH> fm  1 1 2 3 5 8 13 21  100 100 300 500 1300 2100  ok
FORTH> hex fm  1 f 2e 333 331 21fe 64 5DC 13FEC 13F24  ok
FORTH> fm  %01 %1 #10 %11 %1001 %1000 #13 $15  100 100 300 900 1300 2100  ok

-marcel

[toc] | [prev] | [next] | [standalone]

#20174

On Sat, 02 Mar 2013 02:48:43 -0500, WJ <w_a_x_man@yahoo.com> wrote:

> Given a sequence of numbers, keep those that are odd and
> multiply them by 100.
>
> Factor:
>
>
> USE: sequences.extras
>
> { 1 1 2 3 5 8 13 21 } [ odd? ] [ 100 * ] filter-map
> { 100 100 300 500 1300 2100 }


Parable:

[ #1 #1 #2 #3 #5 #8 #13 #21 ] array-from-quote
[ odd? ] array-filter [ #10 * ] array-map


Retro:

needs array'
needs math'
with| array' math' |

create results 100 allot
new{ 1 1 2 3 5 8 13 21 }
[ dup odd? [ 100 * @results results + 1+ ! results ++ ] ifTrue ] apply
results display


-- crc

[toc] | [prev] | [next] | [standalone]

#20176

On 02.03.2013 17:18, Charles Childers wrote:
> On Sat, 02 Mar 2013 02:48:43 -0500, WJ <w_a_x_man@yahoo.com> wrote:
>
>> Given a sequence of numbers, keep those that are odd and
>> multiply them by 100.
>>
>> Factor:
>>
>>
>> USE: sequences.extras
>>
>> { 1 1 2 3 5 8 13 21 } [ odd? ] [ 100 * ] filter-map
>> { 100 100 300 500 1300 2100 }
>
>
> Parable:
>
> [ #1 #1 #2 #3 #5 #8 #13 #21 ] array-from-quote
> [ odd? ] array-filter [ #10 * ] array-map
>
>
> Retro:
>
> needs array'
> needs math'
> with| array' math' |
>
> create results 100 allot
> new{ 1 1 2 3 5 8 13 21 }
> [ dup odd? [ 100 * @results results + 1+ ! results ++ ] ifTrue ] apply
> results display
>
>
> -- crc

I am pretty sure Ruby or Haskell could do it even shorter

AND  !!!

more readable.  ;-)))

[toc] | [prev] | [next] | [standalone]

#20223

A. K. <akk@nospam.org> wrote:
> On 02.03.2013 17:18, Charles Childers wrote:
> > On Sat, 02 Mar 2013 02:48:43 -0500, WJ <w_a_x_man@yahoo.com> wrote:
> >
> >> Given a sequence of numbers, keep those that are odd and
> >> multiply them by 100.
> >>
> >> Factor:
> >>
> >>
> >> USE: sequences.extras
> >>
> >> { 1 1 2 3 5 8 13 21 } [ odd? ] [ 100 * ] filter-map
> >> { 100 100 300 500 1300 2100 }
> >
> >
> > Parable:
> >
> > [ #1 #1 #2 #3 #5 #8 #13 #21 ] array-from-quote
> > [ odd? ] array-filter [ #10 * ] array-map
> >
> >
> > Retro:
> >
> > needs array'
> > needs math'
> > with| array' math' |
> >
> > create results 100 allot
> > new{ 1 1 2 3 5 8 13 21 }
> > [ dup odd? [ 100 * @results results + 1+ ! results ++ ] ifTrue ] apply
> > results display
> >
> >
> > -- crc
> 
> I am pretty sure Ruby or Haskell could do it even shorter
> 
> AND  !!!
> 
> more readable.  ;-)))

Not much shorter I guess. E.g. in Haskell you could use

map (100*) $ filter odd [1,1,2,3,5,8,13,21]

which is quite close to the Factor example, or you could use

[ 100*x | x <- [1,1,2,3,5,8,13,21], odd x ]

which is perhaps the most readable to non-programmers.

And of course there is always Postscript:

[ [1 1 2 3 5 8 13 21] {dup 2 mod 0 eq {pop} {100 mul} ifelse} forall ]

But I do not see much difference in terms of readability, except that
Forth solutions may need to set up the data structures explicitly.
And I was surprised that Retroforth now has an array notation similar
to Postcript; I did not have time to follow its development in recent
years, it looks very interesting.

-- 
Marc

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.forth

csiph-web