Function expand

src/compute-engine/boxed-expression/expand.ts:198–222

(expr: Expression)

  return result;
}

/** Apply the distributive law if the expression is a product of sums.
 * For example, a(b + c) = ab + ac
 * Expand the expression if it is a power of a sum.
 * Expand the terms of the expression if it is a sum or negate.
 * If the expression is a fraction, expand the numerator.
 * If the exression is a relational operator, expand the operands.
 * Return null if the expression cannot be expanded.
 */
export function expand(expr: Expression): Expression {
  // To expand an expression, we need to use its canonical form
  expr = expr.canonical;

  if (typeof expr.operator !== 'string') return expr;

  //
  // Expand relational operators
  //
  if (isRelationalOperator(expr.operator)) {
    const ops = isFunction(expr) ? expr.ops : [];
    return expr.engine._fn(
      expr.operator,
      ops.map((x) => expand(x))
    );
  }

  return (
    expandFunction(