Re: [Factor-talk] Accumulation of subsequences

[Alexander Ilin]

Hello, Björn!

  Thank you, that's exactly what I was looking for!

16.12.2016, 16:01, "Björn Lindqvist" :
> I think you can use group-by from sequences.extras. It works similar
> to map-runs:
>
> { 1 5 "hello" 2 "world" 3 6 9 "!" } [ integer? ] group-by [ swap [ sum
> ] [ first ] if ] { } assoc>map .
> { 6 "hello" 2 "world" 18 "!" }

---=--- 
 Александр

--
Check out the vibrant tech community on one of the world's most 
engaging tech sites, SlashDot.org! http://sdm.link/slashdot
___
Factor-talk mailing list
Factor-talk@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/factor-talk

Re: [Factor-talk] Accumulation of subsequences

[Björn Lindqvist]

I think you can use group-by from sequences.extras. It works similar
to map-runs:

{ 1 5 "hello" 2 "world" 3 6 9 "!" } [ integer? ] group-by [ swap [ sum
] [ first ] if ] { } assoc>map .
{ 6 "hello" 2 "world" 18 "!" }


2016-12-16 11:16 GMT+01:00 Alexander Ilin :
> Hello!
>
>   I was solving this issue, and it got me wondering if there is a better 
> solution somewhere in the library. Could you check this out?
>
>   I want to find consecutive runs of numbers and replace them with a sum, 
> while preserving all other objects in the sequence (currently only strings 
> are in there). For example:
>
> IN: { 1 5 "hello" 2 "world" 3 6 9 "!" } collapse-numbers
> OUT: { 6 "hello" 2 "world" 18 "!" }
>
>   Here's the `collapse-numbers` implementation that I came up with:
>
> :: collapse-numbers ( seq -- seq' )
> f :> accum! seq [
> accum 2dup [ number? ] both? [
> + accum! f
> ] [
> swap accum!
> ] if
> ] map sift accum suffix ;
>
>   Using a local variable for a side-effect in map feels like cheating, 
> straight from my imperative programming background.
>   Is there a way to, maybe, convert numbers into subsequences?
>
> IN: { 1 5 "hello" 2 "world" 3 6 9 "!" } [ number? ] map-runs
> OUT: { { 1 5 } "hello" { 2 } "world" { 3 6 9 } "!" }
>
>   If we had something like `map-runs`, the whole task could be solved in a 
> more functional way:
>
> : collapse-numbers ( seq -- seq' )
> [ number? ] map-runs [ dup string? [ sum ] unless ] map ;
>
>   What are your thoughts on this? Do we **have** something like `map-runs`? 
> Do we **need** it? Should I have used PEGs to parse the sequence?
>
> ---=---
>  Александр
>
> --
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
> ___
> Factor-talk mailing list
> Factor-talk@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/factor-talk



-- 
mvh/best regards Björn Lindqvist

--
Check out the vibrant tech community on one of the world's most 
engaging tech sites, SlashDot.org! http://sdm.link/slashdot
___
Factor-talk mailing list
Factor-talk@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/factor-talk

[Factor-talk] Accumulation of subsequences

[Alexander Ilin]

Hello!

  I was solving this issue, and it got me wondering if there is a better 
solution somewhere in the library. Could you check this out?

  I want to find consecutive runs of numbers and replace them with a sum, while 
preserving all other objects in the sequence (currently only strings are in 
there). For example:

IN: { 1 5 "hello" 2 "world" 3 6 9 "!" } collapse-numbers
OUT: { 6 "hello" 2 "world" 18 "!" }

  Here's the `collapse-numbers` implementation that I came up with:

:: collapse-numbers ( seq -- seq' )
f :> accum! seq [
accum 2dup [ number? ] both? [
+ accum! f
] [
swap accum!
] if
] map sift accum suffix ;

  Using a local variable for a side-effect in map feels like cheating, straight 
from my imperative programming background.
  Is there a way to, maybe, convert numbers into subsequences?

IN: { 1 5 "hello" 2 "world" 3 6 9 "!" } [ number? ] map-runs
OUT: { { 1 5 } "hello" { 2 } "world" { 3 6 9 } "!" }

  If we had something like `map-runs`, the whole task could be solved in a more 
functional way:

: collapse-numbers ( seq -- seq' )
[ number? ] map-runs [ dup string? [ sum ] unless ] map ;

  What are your thoughts on this? Do we **have** something like `map-runs`? Do 
we **need** it? Should I have used PEGs to parse the sequence?

---=--- 
 Александр

--
Check out the vibrant tech community on one of the world's most 
engaging tech sites, SlashDot.org! http://sdm.link/slashdot
___
Factor-talk mailing list
Factor-talk@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/factor-talk