State Transformer

[Theodore Norvell]

> DIY monads are good when: you fix the state variables, you don't want
> to mention them in subprogram parameters.

I've taken this solution for a fairly large piece of software.
One word of warning about DIY state monads, you have to be very carefull
about strictness and lazyness.  If your monad or state are at all lazy,
you can end up dragging a lot of old states around.  When you construct a new
state, you want to be sure that it contains no unevaluated references to
a previous state!

Cheers,
Theodore Norvell

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Dr. Theodore Norvell                                           theo@engr.mun.ca
Electrical and Computer Engineering                http://www.engr.mun.ca/~theo
Engineering and Applied Science
Memorial University of Newfoundland
St. John's, NF, Canada, A1B 3X5

Currently visiting the Department of Computer Science and ICICS at the
University of British Columbia. See my webpage for contact details.