lambda.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

#######################################################################
#
# An example of using the new Excel LAMBDA() function with the
# WriteXLSX rubygem. Note, this function is only currently available
# if you are subscribed to the Microsoft Office Beta program.
#
# Copyright 2000-2021, John McNamara, jmcnamara@cpan.org
# convert to ruby by Hideo NAKAMURA, nakamura.hideo@gmail.com
#

require 'write_xlsx'

workbook = WriteXLSX.new('lambda.xlsx')
worksheet = workbook.add_worksheet

worksheet.write(
  'A1',
  'Note: Lambda functions currently only work with the Beta Channel versions of Excel 365'
)

# Write a Lambda function to convert Fahrenheit to Celsius to a cell.
#
# Note that the lambda function parameters must be prefixed with
# "_xlpm.". These prefixes won't show up in Excel.
worksheet.write('A2', '=LAMBDA(_xlpm.temp, (5/9) * (_xlpm.temp-32))(32)')

# Create the same formula (without an argument) as a defined name and use that
# to calculate a value.
#
# Note that the formula name is prefixed with "_xlfn." (this is normally
# converted automatically by write_formula but isn't for defined names)
# and note that the lambda function parameters are prefixed with
# "_xlpm.". These prefixes won't show up in Excel.
workbook.define_name(
  'ToCelsius',
  '=_xlfn.LAMBDA(_xlpm.temp, (5/9) * (_xlpm.temp-32))'
)
worksheet.write_dynamic_array_formula('A3', '=ToCelsius(212)')

workbook.close