Class: Seq::Lazy

Inherits:
Seq
  • Object
show all
Defined in:
lib/seq/lazy.rb

Overview

Lazy seqs evaluate a block to determine the next value when needed, this value is then saved.

Examples:


s = Seq::Lazy.new([1]) { 1 }
s.take(3) #=> [1, 1, 1]

ns = Seq::Lazy.new([1]) {|l| l[-1] + 1 }
ns.take(5) #=> [1, 2, 3, 4, 5]

fibs = Seq::Lazy.new([1, 1]) {|l| l[-1] + l[-2] }
fibs.take(7) #=> [1, 1, 2, 3, 5, 8, 13]
fibs.take!(7) #=> [21, 34, 55, 89, 144, 233, 377]
fibs.take!(2) #=> [21, 34]

Constant Summary

Constants inherited from Seq

VERSION

Instance Method Summary collapse

Methods inherited from Seq

#each, #ended?, #entries, #inc, #infinite?, #method_missing, #to_a

Constructor Details

#initialize(list = [], items = Float::INFINITY, offset = 0, default = nil) {|list| ... } ⇒ Lazy

Creates a new Lazy seq instance.

Parameters:

  • list (Array) (defaults to: []) —

    Starting values

  • items (Integer) (defaults to: Float::INFINITY) —

    Number of values to return

  • offset (Integer) (defaults to: 0) —

    Index of item to start at

  • default (Object) (defaults to: nil) —

    Value to return when finished cycling

Yields:

  • (list) —

    Block to be called which returns the next value in the list

Yield Parameters:

  • list (Array) —

    The list calculated up to the current point



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# File 'lib/seq/lazy.rb', line 32

def initialize(list=[], items=Float::INFINITY, offset=0, default=nil, &block)
  @list    = list
  @items   = items
  @block   = block
  @offset  = offset
  @default = default

  self.reset
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class Seq

Instance Method Details

#next ⇒ Object

Returns Until ended it returns the next item from list if it exists or calculates it then stores it in list, if ended it returns the default value.

Returns:

  • (Object) —

    Until ended it returns the next item from list if it exists or calculates it then stores it in list, if ended it returns the default value.



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# File 'lib/seq/lazy.rb', line 59

def next
  if ended?
    @default
  else
    @index += 1
    if @index-1 < @list.size
      @list[@index-1]
    else
      @list[@index-1] = @block.call(@list)
    end
  end
end

#reset ⇒ Object

Resets the state of the lazy seq. It also calculates any values necessary to get to the offset.



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# File 'lib/seq/lazy.rb', line 44

def reset
  @index  = @list.size
  @cycles = 0

  until @list.size >= @offset
    @list[@index] = @block.call(@list[0..@index-1])
    @index += 1
  end

  @index = @offset
end