rgchris

This is something of a noodling around that may be of use/interest to someone. It loosely uses Rebol's operator semantics to somewhat intuitively generate LaTeX equation notation. It is by no means comprehensive, I had a use for it and it serves that purpose.

Of interest is the redefinition of math operators as they are known in Rebol and while they are still largely semantically compatible with their common function, they accumulate values as LaTeX notation instead of evaluating them.

Note the handling of blocks and groups (parens). To create intentionally parenthesized content, blocks are required; to manage Rebol's semantics without creating parenthesized content, use groups (parens).

e ^ 1 + x    ; => {e}^{1}+{x}
e ^ (1 + x)  ; => {e}^{1+{x}}
e ^ [1 + x] ; => {e}^{\left(1+{x}\right)}

rgchris

This is a non-exhaustive list of some of things I've encountered in the past year of switching:

• Contexts: Rebol 2 had three types of word spaces—SYSTEM/WORDS, OBJECT! and FUNCTION!. Rebol 3 tries to separate this out a bit with a runtime library (LIB) that contains all the 'standard' functions, SYSTEM/CONTEXTS/USER which is where all the regular script words go and imports meanings from LIB as it encounters new words, and MODULES that are kind of like extended objects designed to keep reusable code segments separate. (I've proposed and am working on some changes as to how that works with external scripts)

• 64-bit integers expand the range of Rebol integers, though does cause a few inconsistencies with bit-shifting (can be a gotcha with some binary formats)

• STRING! types now use multi-byte codepoints—in Oldes' Rebol 3 they are now UTF-8. W

rgchris

Rebol [
    Title: "Mesh Gradients"
    Author: "Christopher Ross-Gill"
    Date: 26-Mar-2026
    Version: 0.1.0
    File: %meshes.reb

    Type: module
    Name: rgchris.meshes
    Exports: [

rgchris

SVG Filters

These examples showcase how to incorporate filters into my SVG creation DSL. Of interest is how language is used to represent the filter pipeline.

MDN describes Filters as akin to layers that stack one on top of the other. I'd suggest it's more like a series of operations that, starting with the target element, take the result of the preceding operation and apply a filter to it. The result of the final operation replaces the target element's initial appearance in the final composition.

Basic Usage

Within the SVG dialect, a filter pipeline is created using the FILTER function. It takes three arguments: an ID (issue!), a margin (pair! or none!), and the sequence of operations (block!). The ID can be used to refer to the filter later on. By default, SVG filters use a margin of 20% of the element's width and height allowing a space for filters to 'bleed'

rgchris

I came across this article, How Designers Should Think About SVG, and was taken by the little whale icon about a third of the way down showcasing the benefits of using SVG for animation. I noticed on clicking through to the CodePen editor that the animation portions were done in CSS. I was curious a) whether the animation could be done in pure SVG/SMIL, and b) whether my Rebol SVG module was up to the task of producing such a file in a reasonably literate fashion. Indeed the animation is doable in SMIL with some caveats, and I believe the generating code to be sufficiently clear in its intent.

Some notes:

• It's not well documented how the additive attribute is required to make multiple transform animations work on a single el

rgchris

Rebol [
    Title: "SVG Sample"
    Needs: [
        r3:rgchris:svg
    ]
]

print svg/encode svg/create 400x400 [
    rectangle #[fill: #myGradient] 20x200 360x180
    circle #[fill: none stroke: #myGradient stroke-width: 10] 160x200 100

rgchris

Iterators, Part I

In this article, I will introduce iterators and discuss how they offer an intuitive interface for addressing a diverse set of programming problems. Specifically, I'll explore the potential application of iterators in Rebol, highlighting how they complement Rebol's elegant and expressive approach to problem-solving.

What are Iterators?

Iterators are mechanisms used to traverse complex data structures without exposing their internal composition. They provide a standard interface for accessing the component parts of those structures sequentially, significantly simplifying the code built around them. Iterators typically share the following characteristics:

• Encapsulation: They encapsulate the domain logic of a given data structure, meaning you do not need to learn that structure to use it.
• Sequential Access: Each call presents the next logical component from that domain.

rgchris

Tree-Walking Iterator

This script features an iterated method of traversing a tree-structure (specifically, a tree created by the Rebol 2 mezzanine PARSE-XML). The iterator returns events—OPEN, CLOSE, EMPTY, and TEXT—upon request until the tree has been fully traversed.

Concept Note

Using an iterated approach to tree traversal allows for fine control of the process that can be dropped and picked up fairly intuitively, effectively reducing the traversal process to a linear stream of events useful for serialization or extraction. This stands in contrast to the callback approach that fully traverses a tree firing callback functions until the tree has been fully traversed.

rgchris

#!/usr/local/bin/rebview -iv

Rebol [
    Title: "Intercepting Key events"
    Author: "Christopher Ross-Gill"
    Date: 23-Feb-2017

    Notes: [
        https://rebolforum.com/index.cgi?f=printtopic&topicnumber=579&archiveflag=archive
    ]

rgchris

Rebol [
    Title: "DSL Example"
    Author: "Christopher Ross-Gill"
    Date: 29-Jan-2023
    Home: https://gist.github.com/rgchris/2a227b6fa3fc9d2ae7fe729ccb09f016
]

reduce-only: func [
    "Evaluates a block of expressions excepting SET-WORD! values"