Module: Stream
Overview
Module Stream defines an interface for an external Iterator which can move forward and backwards. See README for more information.
The functionality is similar to Smalltalk’s ReadStream.
Defined Under Namespace
Classes: BasicStream, CollectionStream, ConcatenatedStream, EmptyStream, EndOfStreamException, FilteredStream, ImplicitStream, IntervalStream, MappedStream, ReversedStream, WrappedStream
Instance Method Summary collapse
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#+(otherStream) ⇒ Object
Create a Stream::ConcatenatedStream by concatenatating the receiver and otherStream.
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#at_beginning? ⇒ Boolean
Returns false if the next #backward will return an element.
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#at_end? ⇒ Boolean
Returns false if the next #forward will return an element.
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#backward ⇒ Object
Move backward one position.
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#collect(&mapping) ⇒ Object
Create a Stream::MappedStream wrapper on self.
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#concatenate ⇒ Object
Create a Stream::ConcatenatedStream on self, which must be a stream of streams.
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#concatenate_collected(&mapping) ⇒ Object
Create a Stream::ConcatenatedStream, concatenated from streams build with the block for each element of self:.
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#create_stream ⇒ Object
create_stream is used for each Enumerable to create a stream for it.
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#current ⇒ Object
Returns the element returned by the last call of #forward.
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#current_edge ⇒ Object
Returns the array [#current,#peek].
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#each ⇒ Object
Implements the standard iterator used by module Enumerable, by calling set_to_begin and basic_forward until at_end? is true.
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#empty? ⇒ Boolean
Returns true if the stream is empty which is equivalent to at_end? and at_beginning? both being true.
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#filtered(&block) ⇒ Object
Return a Stream::FilteredStream which iterates over all my elements satisfying the condition specified by the block.
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#first ⇒ Object
Returns the first element of the stream.
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#forward ⇒ Object
Move forward one position.
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#last ⇒ Object
Returns the last element of the stream.
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#modify(&block) ⇒ Object
Create a Stream::ImplicitStream which wraps the receiver stream by modifying one or more basic methods of the receiver.
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#move_backward_until ⇒ Object
Move backward until the boolean block is not false and returns the element found.
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#move_forward_until ⇒ Object
Move forward until the boolean block is not false and returns the element found.
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#peek ⇒ Object
Returns the element returned by the last call of #backward.
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#remove_first ⇒ Object
Returns a Stream::ImplicitStream wrapping a Stream::FilteredStream, which eliminates the first element of the receiver.
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#remove_last ⇒ Object
Returns a Stream which eliminates the first element of the receiver.
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#reverse ⇒ Object
Create a Stream::ReversedStream wrapper on self.
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#set_to_begin ⇒ Object
Position the stream before its first element, i.e.
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#set_to_end ⇒ Object
Position the stream behind its last element, i.e.
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#unwrapped ⇒ Object
A Stream::WrappedStream should return the wrapped stream unwrapped.
Instance Method Details
#+(otherStream) ⇒ Object
Create a Stream::ConcatenatedStream by concatenatating the receiver and otherStream
(%w(a b c).create_stream + [4,5].create_stream).to_a ==> ["a", "b", "c", 4, 5]
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# File 'lib/stream.rb', line 537 def + (otherStream) [self, otherStream].create_stream.concatenate end |
#at_beginning? ⇒ Boolean
Returns false if the next #backward will return an element.
20 |
# File 'lib/stream.rb', line 20 def at_beginning?; raise NotImplementedError; end |
#at_end? ⇒ Boolean
Returns false if the next #forward will return an element.
17 |
# File 'lib/stream.rb', line 17 def at_end?; raise NotImplementedError; end |
#backward ⇒ Object
Move backward one position. Returns the source of current_edge. Raises Stream::EndOfStreamException if at_beginning? is true.
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# File 'lib/stream.rb', line 31 def backward raise EndOfStreamException if at_beginning? basic_backward end |
#collect(&mapping) ⇒ Object
Create a Stream::MappedStream wrapper on self. Instead of returning the stream element on each move, the value of calling mapping is returned instead. See Stream::MappedStream for examples.
520 |
# File 'lib/stream.rb', line 520 def collect (&mapping); MappedStream.new(self, &mapping); end |
#concatenate ⇒ Object
Create a Stream::ConcatenatedStream on self, which must be a stream of streams.
523 |
# File 'lib/stream.rb', line 523 def concatenate; ConcatenatedStream.new self; end |
#concatenate_collected(&mapping) ⇒ Object
Create a Stream::ConcatenatedStream, concatenated from streams build with the block for each element of self:
s = [1, 2, 3].create_stream.concatenate_collected { |i|
[i,-i].create_stream
}.
s.to_a ==> [1, -1, 2, -2, 3, -3]
532 |
# File 'lib/stream.rb', line 532 def concatenate_collected (&mapping); self.collect(&mapping).concatenate; end |
#create_stream ⇒ Object
create_stream is used for each Enumerable to create a stream for it. A Stream as an Enumerable returns itself.
116 |
# File 'lib/stream.rb', line 116 def create_stream; self end |
#current ⇒ Object
Returns the element returned by the last call of #forward. If at_beginning? is true self is returned.
84 |
# File 'lib/stream.rb', line 84 def current; at_beginning? ? self : basic_current; end |
#current_edge ⇒ Object
Returns the array [#current,#peek].
91 |
# File 'lib/stream.rb', line 91 def current_edge; [current,peek]; end |
#each ⇒ Object
Implements the standard iterator used by module Enumerable, by calling set_to_begin and basic_forward until at_end? is true.
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# File 'lib/stream.rb', line 107 def each set_to_begin until at_end? yield basic_forward end end |
#empty? ⇒ Boolean
Returns true if the stream is empty which is equivalent to at_end? and at_beginning? both being true.
103 |
# File 'lib/stream.rb', line 103 def empty?; at_end? and at_beginning?; end |
#filtered(&block) ⇒ Object
Return a Stream::FilteredStream which iterates over all my elements satisfying the condition specified by the block.
512 |
# File 'lib/stream.rb', line 512 def filtered (&block); FilteredStream.new(self,&block); end |
#first ⇒ Object
Returns the first element of the stream. This is accomplished by calling set_to_begin and #forward, which means a state change.
95 |
# File 'lib/stream.rb', line 95 def first; set_to_begin; forward; end |
#forward ⇒ Object
Move forward one position. Returns the target of current_edge. Raises Stream::EndOfStreamException if at_end? is true.
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# File 'lib/stream.rb', line 24 def forward raise EndOfStreamException if at_end? basic_forward end |
#last ⇒ Object
Returns the last element of the stream. This is accomplished by calling set_to_begin and #backward, which means a state change.
99 |
# File 'lib/stream.rb', line 99 def last; set_to_end; backward; end |
#modify(&block) ⇒ Object
Create a Stream::ImplicitStream which wraps the receiver stream by modifying one or more basic methods of the receiver. As an example the method remove_first uses #modify to create an ImplicitStream which filters the first element away.
544 |
# File 'lib/stream.rb', line 544 def modify (&block); ImplicitStream.new(self, &block); end |
#move_backward_until ⇒ Object
Move backward until the boolean block is not false and returns the element found. Returns nil if no object matches.
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# File 'lib/stream.rb', line 74 def move_backward_until until at_beginning? element = basic_backward return element if yield(element) end nil end |
#move_forward_until ⇒ Object
Move forward until the boolean block is not false and returns the element found. Returns nil if no object matches.
This is similar to #detect, but starts the search from the current position. #detect, which is inherited from Enumerable uses #each, which implicitly calls #set_to_begin.
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# File 'lib/stream.rb', line 64 def move_forward_until until at_end? element = basic_forward return element if yield(element) end nil end |
#peek ⇒ Object
Returns the element returned by the last call of #backward. If at_end? is true self is returned.
88 |
# File 'lib/stream.rb', line 88 def peek; at_end? ? self : basic_peek; end |
#remove_first ⇒ Object
Returns a Stream::ImplicitStream wrapping a Stream::FilteredStream, which eliminates the first element of the receiver.
(1..3).create_stream.remove_first.to_a ==> [2,3]
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# File 'lib/stream.rb', line 550 def remove_first i = 0 filter = self.filtered { | element | i += 1; i > 1 } filter.modify { |s| s.set_to_begin_proc = proc {filter.set_to_begin; i = 0} } end |
#remove_last ⇒ Object
Returns a Stream which eliminates the first element of the receiver.
(1..3).create_stream.remove_last.to_a ==> [1,2]
Take a look at the source. The implementation is inefficient but elegant.
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# File 'lib/stream.rb', line 563 def remove_last self.reverse.remove_first.reverse # I like this one end |
#reverse ⇒ Object
Create a Stream::ReversedStream wrapper on self.
515 |
# File 'lib/stream.rb', line 515 def reverse; ReversedStream.new self; end |
#set_to_begin ⇒ Object
Position the stream before its first element, i.e. the next #forward will return the first element.
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# File 'lib/stream.rb', line 38 def set_to_begin until at_beginning?; basic_backward; end end |
#set_to_end ⇒ Object
Position the stream behind its last element, i.e. the next #backward will return the last element.
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# File 'lib/stream.rb', line 44 def set_to_end until at_end?; basic_forward; end end |
#unwrapped ⇒ Object
A Stream::WrappedStream should return the wrapped stream unwrapped. If the stream is not a wrapper around another stream it simply returns itself.
120 |
# File 'lib/stream.rb', line 120 def unwrapped; self; end |