Module: System::Collections::FoldableStreamLambdas

Included in:

F

Defined in:

lib/raskell/f.rb

Instance Method Summary

• #bucket_by ⇒ Object
• #bucket_by_and_summarize ⇒ Object
• #foldleft ⇒ Object
• #foldr ⇒ Object
• #partition_by ⇒ Object

Instance Method Details

#bucket_by ⇒ Object

# File 'lib/raskell/f.rb', line 319

def bucket_by
  @@bucket_by||= ->(fn, xs) {
    foldl.(->(acc, el) { 
        key = fn.(el)
        acc[key] ||= []
        acc[key] << el
        acc 
      }, {}).(to_stream.(xs))
  }
end

#bucket_by_and_summarize ⇒ Object

# File 'lib/raskell/f.rb', line 330

def bucket_by_and_summarize
  @@bucket_by_and_summarize||= ->(group_fn, summary_fn) {
    map.(summary_fn) * bucket_by.(group_fn)
  }
end

#foldleft ⇒ Object

# File 'lib/raskell/f.rb', line 272

def foldleft
  @@foldleft||= ->(f,u) { 
  
    ->(stream) {
      next_item = stream.next_item
      result = u
      while next_item != [:done]
        if next_item.first == :skip
          
        elsif next_item.first == :yield
          result = f.(result, next_item[1])
        else
          raise "#{next_item} is a malformed stream response"
        end
        next_item = next_item.last.next_item
      end
      result  
    } * to_stream
  
  }
end

#foldr ⇒ Object

# File 'lib/raskell/f.rb', line 294

def foldr
  @@foldr||= ->(f,u) { 
    ->(stream) {
      next_item = stream.next_item
      if next_item == [:done]
        u
      elsif next_item.first == :skip 
        foldr.(f, u, next_item.last)
      elsif next_item.first == :yield
        f.(next_item[1], foldr.(f, u, next_item.last))
      else
        raise "#{next_item} is improperly formed for a Stream"
      end
    } * to_stream
      
  }
end

#partition_by ⇒ Object

# File 'lib/raskell/f.rb', line 312

def partition_by
  @@partition_by||= ->(fn) {
    folded_filter = ->(f) { foldl.(->(acc, el) { f.(el) ?  acc << el : acc }, []) }
    (folded_filter.(fn) + folded_filter.(->(x) { !fn.(x) })) * to_stream
  }
end