Mailing List Archive: 49091 messages
  • Home
  • Script library
  • AltME Archive
  • Mailing list
  • Articles Index
  • Site search

[REBOL] Re: REBOL dynamic graph code problems and REBOL mindset

From: moliad::gmail::com at: 21-Feb-2008 17:19

hi john, I love helping out on these simple (for me hehe) graphic problems, helping others see just how rebol's internal graph engine really is. so I put a little bit of time during break and thought I'd give you a push in the right direction... :-) here is a full application which has (If I understood your post correctly) everything working. look at it, and feel free to ask anything that you are not shure on why or how. Note, there are MANY other ways to do this, faster and/or with less code, but for your learning experience, I added (IMHO)just enough REBOL-specificities to help you 'get it, without going all the way and loosing you. one thing of note is the use of the 'any and 'all functions. although not specifically needing here, this was a good case of showing how to use them, and how they actually can be simpler than a slew of nested if conditions ( 'either, within rebol, as you must know) one comment I will add, is that series manipulation in rebol is very different from other language. every series is mutable, and most series operation are "in-place" meaning, they dont returns a new series, they actualy modifiy the one you specify. for blocks this gets a little confusing, and is probably the biggest thing to get in rebol. once you 'get it, you'll see doors unfolding on how to use rebol. the biggest thing to remember is that when you assign a block, you are not assigning a copy of that block, but the same block over and over, so to make sure copy it if that is really what you want (even when its an empty block, shown in the plot-curve function below). another big one is that the various series function (append, insert, find, etc) have dual natures for block series. Many operations could logically act on or with the block itself, OR its content. this is another thing which must be 'gotten' or else you WILL pull your hair out... hell even after almost a decade, it still bites you sometimes. hehe. so, to solve the issue, REBOL implements a refinement which is named consistantly over all functions which has a duality in meaning (with blocks or others). the refinement is called '/ONLY . if you look at the code, you will see that I use in some instances, and in others I dont' for appending data, the difference is not trivial. this example will illustrate better than words can: a: [1 2 3] b: [4 5 6] append a b == [1 2 3 4 5 6] append/only a b == [1 2 3 [4 5 6]] so often, you'll use a master block like so: c: [] append c a append c b == [[1 2 3][4 5 6]] or using another (very practical) function c: reduce [a b] == [[1 2 3] [4 5 6]] hope this helps you get started in a better position to tackle your actual project :-D -MAx now, the script: ;------------------------------------------------------------------------------------------------------- rebol [ title: "selective curve plot example" author: "Maxim Olivier-Adlhoch" date: 2008-02-21 ] ; GLOBAL STORAGE OF CURVES curves: [] visible-curves: [] curves-fx: [] graph-size: 1000x500 random/seed to-string now/precise plot-curve: func [color /local data x plot][ data: copy [] i: 250 loop graph-size/x [append data i: i + ((random 9) - 5)] plot: copy compose [pen (color) line] x: 10 foreach y data [append plot as-pair x y x: x + 1 ] return plot ] toggle-curve: func [curve /local c][ ; since this is a simple test. ; in a more complete script, you might want to have a proper ; data storage model. ; ; something like a block(list) of objects, which define each curve ; and its state... (color, points, visibility, scale, etc) ; you'd then iterate over this list and rebuild the list any [ all [ c: find/only visible-curves curve remove c ] append/only visible-curves curve ] refresh-graph ] refresh-graph: has [curve] [ clear curves-fx foreach curve visible-curves [ append curves-fx curve ] show the_box ] ; pre-generate 3 curves ; we use the /only refinement to let append know that ; it should adds the block containing the curve data ; into the curves list, instead it its content. append/only curves red-curve: plot-curve red 5 append/only curves green-curve: plot-curve green 5 append/only curves blue-curve: plot-curve blue 5 append/only visible-curves red-curve append/only visible-curves green-curve append/only visible-curves blue-curve graph_view: layout [ the_box: box snow 1000x500 effect reduce ['draw curves-fx] return rstate: toggle on red [toggle-curve red-curve] gstate: toggle on green [toggle-curve green-curve] bstate: toggle on blue [toggle-curve blue-curve] ] ; we want the view to show the curves on startup refresh-graph view graph_view ;------------------------------------------------------------------------------------------------------- On Thu, Feb 21, 2008 at 4:15 AM, John Shea <> wrote: