9.3  Example Constraint Handlers

All example files are in the subdirectory lib/chr of the installation-directory of ECLⁱPS^e (which can be found using get_flag(installation_directory,Dir). The files (.chr, .pl, examples) relevant to a particular constraint system can be found by looking at all files that match the pattern given in the following listing with each example handler. The examples include a colour graphic demo about optimal sender placement for wire-less devices in buildings and company sites, small constraint handlers for

• minimum, maximum of and inequalities between terms (*minmax*),
• terms (functor/3, arg/3, =.. as constraints) (*term*),
• lists (similar to Prolog III) (*list*),
• rational trees (*tree*),
• sound if-then-else, negation and checking, lazy conjunction and disjunction (*control*),
• geometric reasoning about rectangles (*demo*),

and larger constraint handlers for

• booleans for propositional logic (*bool*),
• finite and infinite domains (inspired by CHIP) (*domain*),
• sets (*set*),
• terminological reasoning (similar to KL-ONE) [8] (*kl-one*),
• temporal reasoning (over time points and intervals) [7] (*time*),
• equation solving over real numbers (similar to CLP(R)) or rational numbers (*math*).

CHRs have also been used as a committed choice programming language on their own (*prime*).

The example handlers can be loaded using chr(lib(File)). For instance the finite domain handler can be made available as follows (the current directory must have write permission so that the pl file can be created):

[eclipse 1]: lib(chr), chr(lib(domain)).
...
domain.pl  compiled traceable 241028 bytes in 1.22 seconds

yes.
[eclipse 2]: X::1..10, X ne 5.

X = X

Constraints:
(4) X_g1165 :: [1, 2, 3, 4, 6, 7, 8, 9, 10]

yes.