@INPROCEEDINGS{Hanus11Assertions,
author    = "Hanus, M.",
title     = "Lazy and Enforceable Assertions for Functional Logic Programs",
year      = "2011",
booktitle = "Proc.\ of the 19th International Workshop on Functional and
             (Constraint) Logic Programming (WFLP 2010)",
pages     = {84-100},
publisher = {Springer LNCS 6559},
abstract = {
Assertions or contracts are an important technique to improve the
quality of software. Thus, assertions are also desirable for
functional logic programming. Unfortunately, there is no
established meaning of assertions in languages with a demand-driven
evaluation strategy. Strict assertions are immediately checked but
may influence the behavior of programs. Lazy assertions do not
modify the behavior but may not be faithful since some assertions
might not be checked at all. In order to avoid the disadvantages
of strict and lazy assertions, we propose enforceable assertions that
are delayed as lazy assertions
but can be explicitly enforced at some point where faith is
required, e.g., at the end of the program execution or before
irrevocable I/O actions.
We describe a prototypical implementation of this
idea in the functional logic language Curry
where the programmer can choose between lazy and enforceable assertions.
}
}