@rulecad/variables

Design values you can trace. Every measurement is a variable, and every variable can say where it comes from: a printer's spec, a standard, a community figure, or something you measured (kind: spec, community, measured or estimate, with its source). Expressions are parsed, never eval'd, so a JSON file can't run code. No dependencies; browsers and Node 20+.

import { resolve } from '@rulecad/variables';

const printer = { name: 'printer', rules: {
  line: { value: 0.42, unit: 'mm', kind: 'spec', source: 'Bambu Lab wiki' },
  wall: { value: 'line * 3' },
} };
const tray = {
  uses: ['printer'],
  variables: {
    wall:   { value: 'printer.wall', label: 'Wall' },
    length: { value: 120, unit: 'mm', tweak: { min: 80, max: 160 } },
    inner:  { value: 'length - 2 * wall' },
  },
};

const { values, entries } = resolve(tray, { sets: { printer }, set: { length: 140 } });
values.inner          // 137.48
entries               // every variable and rule with its value, source and whether anything used it

• Expressions: + - * /, brackets, min, max, round(x, step), and sind/cosd/tand in degrees, over numbers and names. evaluate(src, lookup) runs one on its own.
• Rule sets are handed in through sets, or fetched by name with load: (name) => … (from files, a URL, anywhere).
• Tweaks: only variables with a tweak range can be set, and only within it. Errors say which variable and why.
• Names, not numbers: choice: [...], type: 'text' or type: 'anchor' (one of ANCHORS: tl tc tr / ml mc mr / bl bc br) hold names, and they're checked too.
• display: values for a lighter on-screen copy (fewer segments, no fine detail). They aren't checked and they don't change what prints.
• lint(source) lists the number literals in a design's code that should be variables. Only 0, 1 and 2 pass, plus anything in comments or strings. It's how "every measurement is a variable" gets checked.