@INPROCEEDINGS{Hanus10WFLP,
author    = "Hanus, M.",
title     = "Lazy and Faithful Assertions for Functional Logic Programs",
year      = "2010",
booktitle = "Proc.\ of the 19th International Workshop on Functional and
             (Constraint) Logic Programming (WFLP 2010)",
pages     = {50-64},
publisher = {Universidad Polit\'ecnica de Madrid},
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.  This paper proposes an intermediate
approach where the user can choose between lazy or faithful
assertions.  In order to avoid disadvantages of faithful assertions,
we propose to delay them until an explicit point where faith is
required, e.g., at the end of the program execution or before I/O
actions.  We describe a prototypical implementation of this
idea in the functional logic language Curry.
}
}