Embedding the engine

import { ExpressionEngine } from "solve-engine";

const engine = new ExpressionEngine("en");

The first argument is the locale, which decides decimal and thousands separators and the ambiguous date order.

Configuration

The second and third arguments enable diagnostics and override configuration. Both are optional.

const engine = new ExpressionEngine("en", false, {
  validation: {
    maxExpressionLength: 1000,
    maxComplexity: 500,
  },
});

Safety limits exist because the engine is designed to run on untrusted input as someone types. They bound expression length, parse complexity, instruction count, stack depth, and how many elements a range or matrix may be expanded to by map/reduce (vm.maxCollectionSize, 100000 by default, which is what stops a typo like sum(x, 1:100000000) from allocating until the host runs out of memory). Each produces a clear error rather than hanging.

Reading a result

import { ValueType } from "solve-engine/vm";

const [value] = engine.evaluateExpression("2 + 2");

value.type;        // ValueType.Number
value.toNumber();  // 4
value.unit;        // undefined

Clearing state

An engine accumulates variables and cached results. Call clear() to reset it between documents rather than constructing a new one, which is cheaper.

engine.clear();