Function parseRange

src/expression/parse.js:979–1027

* parse range, "start:end", "start:step:end", ":", "start:", ":end", etc * @return {Node} node * @private

(state)

   * @private
   */
  function parseRange (state) {
    let node
    const params = []

    if (state.token === ':') {
      if (state.conditionalLevel === state.nestingLevel) {
        // we are in the midst of parsing a conditional operator, so not
        // a range, but rather an empty true-expr, which is considered a
        // syntax error
        throw createSyntaxError(
          state,
          'The true-expression of a conditional operator may not be empty')
      } else {
        // implicit start of range = 1 (one-based)
        node = new ConstantNode(1)
      }
    } else {
      // explicit start
      node = parseAddSubtract(state)
    }

    if (state.token === ':' && (state.conditionalLevel !== state.nestingLevel)) {
      // we ignore the range operator when a conditional operator is being processed on the same level
      params.push(node)

      // parse step and end
      while (state.token === ':' && params.length < 3) { // eslint-disable-line no-unmodified-loop-condition
        getTokenSkipNewline(state)

        if (state.token === ')' || state.token === ']' || state.token === ',' || state.token === '') {
          // implicit end
          params.push(new SymbolNode('end'))
        } else {
          // explicit end
          params.push(parseAddSubtract(state))
        }
      }

      if (params.length === 3) {
        // params = [start, step, end]
        node = new RangeNode(params[0], params[2], params[1]) // start, end, step
      } else { // length === 2
        // params = [start, end]
        node = new RangeNode(params[0], params[1]) // start, end
      }
    }

    return node
  }

  /**
   * add or subtract