''Purely Functional Data Structures'' by Chris Okasaki. Cambridge University Press 1998. 

Actually, the book is not online, but the Ph.D dissertation that morphed into the book is:

http://www-2.cs.cmu.edu/~rwh/theses/okasaki.pdf

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Is this the counterpart to dysfunctional data structures?

''There is certainly something disfunctional about the discussion of it. I found the actual book first and then this page, which was an orphan until I adopted it and gave it some links. So I know nothing of how it came to be here, where FunctionalProgramming is a topic. As to the name, I did not invent it.'' -- JohnFletcher

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Chris Okasaki's reflections ten years on from the book version:

http://okasaki.blogspot.co.uk/2008/02/ten-years-of-purely-functional-data.html

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This page: http://www.erlang.org/doc/man/queue.html has an implementation of a queue in ErlangLanguage. This includes what is termed the '''Okasaki API''' at the bottom of the page which treats a queue as a list. -- JohnFletcher
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I have found a lot of ideas in this book and want to label it as a BookStart for me. -- JohnFletcher
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See also PurelyFunctional
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CategoryBook CategoryOnlineBook CategoryFunctionalProgramming CategoryHaskell