Function dictionaryFromExpression

src/math-json/utils.ts:219–250

(
  expr: MathJsonExpression | null
)

// - a `Dictionary` expression
// - a `KeyValuePair` or `Tuple` expression
export function dictionaryFromExpression(
  expr: MathJsonExpression | null
): null | MathJsonDictionaryObject {
  if (expr === null) return null;

  if (isDictionaryObject(expr)) return expr as MathJsonDictionaryObject;

  // Is it a KeyValuePair or Tuple expression?
  const kv = keyValuePair(expr);
  if (kv)
    return {
      dict: { [kv[0]]: expressionToDictionaryValue(kv[1]) ?? 'Nothing' },
    } as unknown as MathJsonDictionaryObject;

  // Is it a Dictionary expression?
  if (operator(expr) === 'Dictionary') {
    const dict: Record<string, DictionaryValue> = {};
    // `operands()` is already 0-based and head-stripped — iterate from the
    // first operand (the loop used to start at 1, silently dropping the first
    // dictionary entry).
    for (const op of operands(expr)) {
      const kv = keyValuePair(op);
      if (kv) {
        dict[kv[0]] = expressionToDictionaryValue(kv[1]) ?? 'Nothing';
      }
    }

    return { dict } as unknown as MathJsonDictionaryObject;
  }

  return null;
}

export function dictionaryFromEntries(
  dict: Record<string, MathJsonExpression>