ruby - 将哈希值乘以一个数字，负值返回 0

Question

如何将哈希的非负数值乘以一个数字(例如:2)，并且对于负值仅返回 0？

例如，使用此哈希(具有可变年份键):

hash = {"year2020" => "-2.0", "year2021" => "3.0", "year2022" => "1.0",...}

结果将是:(-2.0 给出 0.0, 3.0*2=6.0, 1.0*2=2.0)

result = {"year2020" => "0.0", "year2021" => "6.0", "year2022" => "2.0",...}

我尝试了这个，但我不知道如何获得 0 而不是负值:

hash.map { |k, v| [k, v.to_f * 2] }.to_h
=> {"year2020"=>-4.0, "year2021"=>6.0, "year2022"=>2.0}

Answer 1

您可以使用Hash#transform_values (在 Ruby v2.4 中引入):

hash = {"year2020"=>"-2.0", "year2021"=>"3.0", "year2022"=>"1.0" }

hash.transform_values { |v| [2*v.to_f, 0].max }
  #=> {"year2020"=>0, "year2021"=>6.0, "year2022"=>2.0}