Solutions to different problems. I proposed a simple generic thing that only composes functions, allowing for transformation of block arg.
Transducers seem like streaming, data-flow specific, thing. Maybe yours helps the original problem in the long run. I just tried to find something to solve more specific part of it while being such generic that it helps in other places as well. Just pointing it out so there isn't a perception they are competing to solve same problem and only one should be selected. Herby On July 3, 2018 3:57:21 PM GMT+02:00, "Steffen Märcker" <merk...@web.de> wrote: >I think, streams and functional composition match up nicely and >transducers are a way to do this. I've introduced them earlier on this > >list. (I hesitated to weight into the discussion, as I won't have time >to >work on the Pharo port of Transducers until October.) > >Let me give a simplified example. I assume the basic messages are >#nextPut: and #close: to write to aStream and close it. > > aString > transduce: LineEndCrLf flatMap > reduce: (#nextPut: completing: #close) > init: aStream > >* Let aString be the source, i.e., some object that yields a sequence >of >characters: > a CR b >* Let LineEndConventionLF a function that maps CR to #(CR LF): > a CR b -> a #(CR LF) b >* #flatMap embeds #(CR LF) into the sequence: > a CR LF b >* (#nextPut: completing: #close) puts each character on the stream and > >calls #close at the end: > aStream > nextPut: $a; > nextPut: CR; > nextPut: LF; > nextPut: $b; > close; > yourself. >* #transduce:reduce:init: actually starts the writing process. > >First, (LineEndConventionLF flatMap) is composable with other >transformations, e.g., encoding. The example above would change to: > > aString > transduce: LineEndCrLf flatMap * EncodeUTF8 flatMap > reduce: (#nextPut: completing: #close) > init: aByteStream > >LineEndCrLf and EncodeUTF8 only have to know how to process single >characters. Hence, they are highly reusable. > >Second, as the source the transformations, the writing process and the > >data sink are distinct objects, we can freely interact with them and >build >arbitrary pipelines. It is straight-forward to come up with other >iteration methods than #reduce:init:, e.g., step-wise processing of >streams. > >Best, Steffen
