Delimited Control in OCaml. Oleg Kiselyov

http://okmij.org/ftp/continuations/caml-shift-journal.pdf

We describe the first implementation of multi-prompt delimited control op-
erators in OCaml that is direct in that it captures only the needed part of the
control stack. The implementation is a library that requires no changes to
the OCaml compiler or run-time, so it is perfectly compatible with existing
OCaml source and binary code.

Backtracking, Interleaving, and Terminating Monad Transformers

http://homes.sice.indiana.edu/ccshan/logicprog/LogicT-icfp2005.pdf

Backtracking, Interleaving, and Terminating Monad Transformers

Oleg Kiselyov, Chung-chieh Shan, Daniel P. Friedman, Amr Sabry

We design and implement a library for adding backtracking com-
putations to any Haskell monad. Inspired by logic programming,
our library provides, in addition to the operations required by the
MonadPlus interface, constructs for fair disjunctions, fair conjunc-
tions, conditionals, pruning, and an expressive top-level interface.
Implementing these additional constructs is easy in models of
backtracking based on streams, but not known to be possible in
continuation-based models. We show that all these additional con-
structs can be generically and monadically realized using a single
primitive msplit. We present two implementations of the library:
one using success and failure continuations; and the other using
control operators for manipulating delimited continuations.