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Re: ANN: A brief introduction to streams ... plus a stream lib

• From: Bjoern Hoehrmann <derhoermi@gmx.net>
• To: "Costello, Roger L." <costello@mitre.org>
• Date: Sat, 11 Sep 2010 21:32:35 +0200

* Costello, Roger L. wrote:
>What distinguishes a stream from an ordinary sequence is delayed evaluation. The idea is
>this: construct a stream only partially and pass the partial construction to the program that
>consumes the stream. If the consumer attempts to access a part of the stream that has not
>yet been constructed, the stream will automatically construct just enough more to produce
>the required part, thus preserving the illusion that the entire stream exists.

When values are obtained only when needed then you have Lazy Evaluation.
That is a concept independent of streams in the general sense. A related
concept is that of an Online Algorithm which can compute partial results
even if all data is not (yet) available. As the term is commonly used,
you can have a stream and not care whether, how and when it is consumed;
for instance a live audio stream may be made available as it is recorded
with no regard if listeners want to hear more or if they can keep up. It
would probably be more accurate to say a stream is simply a sequence for
which no length has been pre-determined, as opposed to a block which is
a sequence of a certain length (see for instance the distinction between
block and stream ciphers in cryptography).
-- 
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
Am Badedeich 7 · Telefon: +49(0)160/4415681 · http://www.bjoernsworld.de
25899 Dagebüll · PGP Pub. KeyID: 0xA4357E78 · http://www.websitedev.de/ 

• References:
  • ANN: A brief introduction to streams ... plus a stream library
    • From: "Costello, Roger L." <costello@mitre.org>