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| class NoSuchElementException < StandardError; end | |
| class Option | |
| def initialize(val) | |
| @val = val | |
| end | |
| def present? | |
| !@val.nil? | |
| end | |
| def map(&block) | |
| if present? | |
| Option(block.call(@val)) | |
| else | |
| Option(nil) | |
| end | |
| end | |
| def flat_map(&block) | |
| if present? | |
| block.call(@val) | |
| else | |
| Option(nil) | |
| end | |
| end | |
| def get_or_else(fallback) | |
| present? ? @val : fallback | |
| end | |
| def to_s | |
| if present? | |
| "#<Option: Some(#{@val})>" | |
| else | |
| "#<Option: None>" | |
| end | |
| end | |
| end | |
| def Option(val) | |
| Option.new(val) | |
| end | |
| Some = -> (val) { val.present? } | |
| None = -> (val) { !val.present? } | |
| opt = Option(2) | |
| case opt | |
| when Some | |
| puts "opt had a present val!" | |
| when None | |
| puts "opt was a blank val" | |
| end | |
| nil_opt = Option(nil) | |
| case nil_opt | |
| when Some | |
| puts "wat" | |
| when None | |
| puts "nil_opt was a blank val" | |
| end | |
| puts Option(2).get_or_else(3) # => 2 | |
| puts Option(nil).get_or_else(3) # => 3 | |
| puts Option(2).map { |x| x * 2 } # => #<Option: Some(4)> | |
| puts Option(2).flat_map { |x| Option(x * 2) } # => #<Option: Some(4)> | |
| puts Option(nil).map { |x| x * 2 } # => #<Option: None> | |
| puts Option(nil).flat_map { |x| Option(x * 2) } # => #<Option: None> |
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