| Class | Generator |
| In: |
generator.rb
|
| Parent: | Object |
Generator converts an internal iterator (i.e. an Enumerable object) to an external iterator.
Note that it is not very fast since it is implemented using continuations, which are currently slow.
Example
require 'generator'
# Generator from an Enumerable object
g = Generator.new(['A', 'B', 'C', 'Z'])
while g.next?
puts g.next
end
# Generator from a block
g = Generator.new { |g|
for i in 'A'..'C'
g.yield i
end
g.yield 'Z'
}
# The same result as above
while g.next?
puts g.next
end
Included Modules
Public Class methods
Creates a new generator either from an Enumerable object or from a block.
In the former, block is ignored even if given.
In the latter, the given block is called with the generator itself, and expected to call the yield method for each element.
# File generator.rb, line 69
69: def initialize(enum = nil, &block)
70: if enum
71: @block = proc { |g|
72: enum.each { |x| g.yield x }
73: }
74: else
75: @block = block
76: end
77:
78: @index = 0
79: @queue = []
80: @cont_next = @cont_yield = @cont_endp = nil
81:
82: if @cont_next = callcc { |c| c }
83: @block.call(self)
84:
85: @cont_endp.call(nil) if @cont_endp
86: end
87:
88: self
89: end
Public Instance methods
Returns the element at the current position.
# File generator.rb, line 141
141: def current()
142: if @queue.empty?
143: raise EOFError, "no more elements available"
144: end
145:
146: @queue.first
147: end
Rewinds the generator and enumerates the elements.
# File generator.rb, line 157
157: def each
158: rewind
159:
160: until end?
161: yield self.next
162: end
163:
164: self
165: end
Returns true if the generator has reached the end.
# File generator.rb, line 102
102: def end?()
103: if @cont_endp = callcc { |c| c }
104: @cont_yield.nil? && @queue.empty?
105: else
106: @queue.empty?
107: end
108: end
Returns the current index (position) counting from zero.
# File generator.rb, line 116
116: def index()
117: @index
118: end
Returns the element at the current position and moves forward.
# File generator.rb, line 126
126: def next()
127: if end?
128: raise EOFError, "no more elements available"
129: end
130:
131: if @cont_next = callcc { |c| c }
132: @cont_yield.call(nil) if @cont_yield
133: end
134:
135: @index += 1
136:
137: @queue.shift
138: end
Returns true if the generator has not reached the end yet.
# File generator.rb, line 111
111: def next?()
112: !end?
113: end
Returns the current index (position) counting from zero.
# File generator.rb, line 121
121: def pos()
122: @index
123: end
Rewinds the generator.
# File generator.rb, line 150
150: def rewind()
151: initialize(nil, &@block) if @index.nonzero?
152:
153: self
154: end