kernelcad-params

kernelCAD — editable parameters

Use param() for values the user may want to tweak after the first build; use literals for incidental dimensions. A param returns a symbolic ParamRef, not a number, so do not do JS arithmetic with it (paramRef / 2 throws feature.invalid-args at the coercion site — the result would be a frozen number that stops re-evaluating on param updates). For derived dimensions, chain the arithmetic methods on the ParamRef itself: .add, .subtract, .multiply, .divide, .negate each return a new ParamRef built on a structured expression that re-evaluates whenever the underlying param changes — e.g. param('r', 5).divide(2) for a half-radius, or param('w', 80).subtract(param('margin', 5).multiply(2)) for a derived inset width.

param() / params() API

// Single named param — returns a symbolic ParamRef<T>.
param<T extends number | boolean>(name: string, defaultValue: T, opts?: {
  min?: number;
  max?: number;
  description?: string;
}): ParamRef<T>;

// Batched shorthand — every key becomes a ParamRef of the same type as
// its default value. Accepts only number and boolean defaults.
params({ width: 60, addCablePort: true }): {
  width: ParamRef<number>;
  addCablePort: ParamRef<boolean>;
};

ParamRef arithmetic

ParamRef is a branded symbolic node. Do not use JS operators; use the chain methods:

Method	Returns	Notes
.add(n)	ParamRef<number>	paramRef.add(5)
.subtract(n)	ParamRef<number>	paramRef.subtract(margin)
.multiply(n)	ParamRef<number>	paramRef.multiply(2)
.divide(n)	ParamRef<number>	paramRef.divide(2)
.negate()	ParamRef<number>	-paramRef symbolic

Each method accepts either a plain number or another ParamRef. Chains stay fully symbolic: radius.multiply(2).add(1) is a ParamRef, not a number, and re-evaluates on each param change.

Usage example

const boltDia = param('boltDia', 5, { min: 3, max: 10, description: 'bolt hole diameter' });
const addCablePort = param('addCablePort', true, { description: 'include cable pass-through' });

return box(80, 50, 6)
  .holes('top', {
    positions: [{ u: -30, v: -20 }, { u: 30, v: -20 }],
    diameter: boltDia,
    depth: 'through',
    name: 'mountBolts',
  })
  .cutout(
    path().moveTo(-8, -5).lineTo(8, -5).lineTo(8, 5).lineTo(-8, 5).close(),
    { face: 'top', depth: 'through', name: 'cablePort', enabled: addCablePort },
  );