Class: ListComprehension

Inherits:
Object
  • Object
show all
Defined in:
lib/ruby_list_comprehension.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ ListComprehension

Returns a new instance of ListComprehension.



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# File 'lib/ruby_list_comprehension.rb', line 10

def initialize
  @cache = {}
  @caching = true
  @version = RUBY_VERSION
  @c = ->x {
    # save a pristine copy of call for caching
    y = x[0..-1]
    # check for cached results
    return @cache[x] if @caching && @cache[x]
    # check for empty call
    return [] if x.empty? || x == "" || x.nil?
    # required length of keywords and spaces is 10
    raise 'syntax error in list comprehension' if x.length < 10
    arr = x.split
    # check for semicolon instead of do, for now I replace back to do for simplicity :()
    if arr[3][-1] == ';' || arr[4][0] == ';' || arr[5][0] == ';' && !arr.include?('do')
      arr = x.to_s.sub(';', ' do ').split
    end

    # pre-eval to check for invalid syntax, hash as iterable, etc.
    begin
      res = instance_eval(x)
      return [] if res.nil?
      raise 'iterable can only be range, set, or array, not hash objects' if res.is_a? Hash
    rescue SyntaxError => se
      raise 'incorrect syntax for list comprehension' + se.to_s
    end
    # raise 'iterable can only be range, set, or array, not hash objects' if eval(x).is_a? Hash


    iterable = arr[3]
    if_condition = arr.include?('if') ? arr[arr.index('if') + 1...-1] : ['true']
    map_condition = arr[arr.index('do') + 1...(arr.index('if') || arr.index('end'))]
    if (map_condition == [arr[1]]) && (if_condition == ['true'] || if_condition == true)
      # p "no method needed"
      res = instance_eval(arr[3])
      return res.is_a?(Array) ? res : [res]
    end
    self.class.send(:define_method,'lc') do |arr|
      if map_condition == [arr[1]]
        # p 'filter'
        return instance_eval(iterable).filter do |x|
          instance_eval(if_condition.join(' '))
        end
      end

      if if_condition == ['true'] || if_condition == true
        # p 'map'
        return instance_eval(iterable).map do |x|
          instance_eval(map_condition.join(' '))
        end
      end
      # check Ruby Version stored in @version
      if @version >= '2.7.0'
        return instance_eval(iterable).filter_map do |x|
          instance_eval(map_condition.join(' ')) if eval(if_condition.join(' '))
        end
      else
        return instance_eval(iterable).map do |x|
          instance_eval(map_condition.join(' ')) if eval(if_condition.join(' ')).compact!
        end
      end
    end
    list_comp = lc(arr)
    list_comp = list_comp.is_a?(Array) ? list_comp : [list_comp]
    @cache[arr] = list_comp
    list_comp
  }
end

Instance Attribute Details

#c ⇒ Object (readonly)

Returns the value of attribute c.



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# File 'lib/ruby_list_comprehension.rb', line 5

def c
  @c
end

#cache ⇒ Object (readonly)

Returns the value of attribute cache.



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# File 'lib/ruby_list_comprehension.rb', line 5

def cache
  @cache
end

#version ⇒ Object (readonly)

Returns the value of attribute version.



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# File 'lib/ruby_list_comprehension.rb', line 5

def version
  @version
end

Instance Method Details

#[](*args) ⇒ Object 



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# File 'lib/ruby_list_comprehension.rb', line 6

def [](*args)
  c[*args]
end