35.4.11 Exceptions

The CHR runtime system reports instantiation and type errors for the predicates:

find_constraint/2

findall_constraints/3

insert_constraint/2

remove_constraint/1

notify_constrained/1

The only other CHR specific runtime error is:

     ! CHR: registering New, module Module already hosts Old

An attempt to load a second handler New into module Module already hosting handler Old was made.

The following exceptional conditions are detected by the CHR compiler:

     ! CHR Compiler: syntax rule N: Term

If the N-th Term in the file being loaded violates the CHR syntax (see CHR Syntax).

     ! CHR Compiler: too many general heads in Name

Unspecific heads in definitions like C \ C <=> true must not be combined with other heads in rule Name.

     ! CHR Compiler: bad pragma Pragma in Name

The pragma Pragma used in rule Name does not qualify. Currently this only happens if Pragma is unbound.

     ! CHR Compiler: found head F/A in Name, expected one of: F/A list

Rule Name has a head of given F/A, which is not among the defined constraints.

     ! CHR Compiler: head identifiers in Name are not unique variables

The identifiers to refer to individual constraints (heads) via `#' in rule Name do not meet the indicated requirements.

     ! CHR Compiler: no handler defined

CHR specific language elements, declarations or rules for example, are used before a handler was defined. This error is usually reported a couple of times, i.e. as often as there are CHR forms in the file expecting the missing definition.

     ! CHR Compiler: compilation failed

Not your fault. Send us a bug report.