[REBOL] Block manipulation: help!
From: mat:plothatching at: 13-Jun-2002 14:05
Here's another newbish type question. I've never really gotten my head
around block/series manipulation in Rebol. As a result of this my code
is full of silly hacks that keep building temporary data structures to
get the results I want.
I was hoping that someone may help my cog drop into place so I can
write some decent Rebol at last.
Here's a typical problem;
Let's say we have a file which is full of cars and the colours they
are available in;
Now what if I want to scan through this file and build up a list of
cars but then just state which colours they are available in after in
the structure. I'll assuming an elegant format is this;
FinalData: make block! [
"Coupe" ["Red" "Yellow"]
"Pickup Truck" ["Red" "Yellow" "Orange" "Blue"]
So, reading the file is easy enough.
CarLines: read/lines %file
foreach CarLine CarLines [
Car: pick (parse CarLine none) 1
Colour: pick (parse CarLine none) 2
The question is, how do I create final data? I can do a find on the
FinalData to see if a car is there already. But all this does is
return the data after. I've always been puzzled about the lack of a
word/function to return the position in a series/block of a find,
So anyhow, here's the best I can think of;
either found? find FinalData Car [
; Already have an entry for this car...
; Select at least allows retrieving of the block following our
; found element easily...
existingcolours: select FinalData Car
; Great so add the new colour to the existing colours
append existingcards Car
; But how do we poke it back? We don't have a position to do a poke?
; Plug in the new car, plug in the block which has the colour in it
append FinalData Car
append FinalData reduce[reduce[Colour]]
I don't really understand the block navigation issues to solve this
problem or to somehow poke more data in without having a position.
As usual any stupid stuff I've missed and elegant solutions