Function match

test/compute-engine/patterns.test.ts:14–35

(
  pattern: ExpressionInput,
  expr: Expression | MathJsonExpression,
  options?: PatternMatchOptions
)

const ce = engine;

function match(
  pattern: ExpressionInput,
  expr: Expression | MathJsonExpression,
  options?: PatternMatchOptions
): Substitution | null {
  // Avoid re-boxing both expr & pattern so as to preserve canonical-status
  expr =
    expr instanceof _BoxedExpression ? (expr as Expression) : ce.expr(expr);
  pattern =
    pattern instanceof _BoxedExpression
      ? (pattern as Expression)
      : ce.expr(pattern);

  const result = expr.match(pattern, {
    useVariations: true,
    ...options,
  });
  if (result === null) return null;
  const r = {};
  for (const key of Object.keys(result)) r[key] = result[key];
  return r;
}

describe('Examples from Patterns and Rules guide', () => {
  const pattern: MathJsonExpression = ['Add', '_', 'x'];