A formula at each record
A Vex program evaluates at one key of a space of records. A field name reads at the focus. An address reads at another key, like a spreadsheet reference.
Vex
Write one formula. Evaluate it at each record. When a value is missing, Vex tells you why.
npm i @mark1russell7/vex @mark1russell7/vex-domainsconst centre = root.from("size") ._.halve()._.add("position"); centre.others((e) => e._.distance( e.from("size")._.halve()._.add("position")));arrow: the nearest other box. red edge: the box overlaps another box. Point at a box to see its list.18 programs in 0.00 ms each frame
Explore
Section titled “Explore”Each page below is interactive. The programs run in your browser, with the same packages that you install from npm.
- The LabWrite a chain and see its result at each record: boxes, a Life grid, a tree or rows.
- The Game of LifeThe rule of Conway is one Vex expression. It evaluates at each cell in each generation.
- Sheets and cyclesCells refer to cells. A cycle gives the error value #CYCLE!, and the other cells stay correct.
- Axes as relationsAn axis goes from the focus to a list of keys. A tree has children, ancestors and descendants.
- Why none?Each error value has a code and a trace. A live example shows where each code starts.
- The law arenafast-check tests the laws of each domain in your browser. It finds a false claim and makes it small.
Boxes on graph paper
Section titled “Boxes on graph paper”Vex started as layout math. A layout engine had boxes with a position and a size, and it asked questions like “does this box overlap another box?” The program below asks that question at each box.
Drag a box. Each program on this page reads the same four boxes, so each one evaluates again. Select an origin to see the program from the view of another box. Move the slider to see each step of the evaluation.
root.from("position")._.add("size")
.others((e) =>
e._.subtract("position")._.allPositive()._.and(
e.from("position")._.add("size")._.subtract(e.origin().from("position"))._.allPositive()))
.any()step 27 of 27
Result at A: true
| origin | A | B | C | D |
|---|---|---|---|---|
| result | true | true | false | false |
What Vex is
Section titled “What Vex is”Axes
The others axis evaluates a body at each other key. The base value comes from the origin, and the fields come from each target.
Error values
Vex does not throw. A failure is an error value with a code, for example #REF! or #N/A, and a trace shows where it started.
Your domains
A domain tells Vex which values belong to it, which ops they have, and which laws the ops obey. Tests check each law.
Use it in your code
Section titled “Use it in your code”Install the core and the domains. Then build a chain over your own records. The chain has the type of its result.
import { space, vex } from "@mark1russell7/vex";import { Vec2, Vec2Domain } from "@mark1russell7/vex-domains";
const A = { position: new Vec2(2, 2), size: new Vec2(5, 4) };const B = { position: new Vec2(6, 5), size: new Vec2(4, 4) };
const separated = vex(Vec2Domain) .over(space.record({ A, B })) .from("position")._.add("size") .other()._.subtract("position") ._.anyNonPositive();
separated.at("A"); // { tag: "some", value: false }separated.explain("A"); // a trace of each stepThe tour adds one call at a time to a chain. The API lists each export, and the specification shows the test status of each requirement.