Programming Language for Old Timers

by David A. Moon
February 2006 .. September 2008

Comments and criticisms to dave underscore moon atsign alum dot mit dot edu.

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Stream Protocol

A stream is a stateful object that effectively combines a sequence and an iteration state for that sequence. Unlike iterating through a sequence, iterating through a stream changes the stream.

The following method requirements constitute the stream protocol:

defprotocol stream
  end?(x is stream) is boolean
  next(x is stream)             ; returns next element
  advance(x is stream)
Their behavior is very similar to the methods of the same names of the sequence protocol. There is no start-iteration method, as this happens automatically when a stream is created. The advance method does not return anything in particular.

There is a pseudo-constructor method stream that takes a sequence and returns a stream that iterates through that sequence.

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