9.3.7 Exceptions

Exceptions are generated by the parser in two cases. The first case is when the user specifies wrong input. For example when specifying

load_structure( string('<m></m>'), Document, [line(xyz)], Warn)

The string xyz is not in the domain of line. Hence in this case a domain error exception will be thrown.

Exceptions are generated when XML being parsed is not well formed. For example if the input XML contains

'<m></m1>'

exceptions will be thrown.

In both cases the format of the exception is

  error( sgml( error term), error message)
  warning( sgml( warning term), warning message)

where error term or warning term can be of the form

• pointer to the parser instance,
• line at which error occurred,
• error code.
• functor(argument), where functor and argument depend on the type of exception raised. For example,

  resource-error(no-memory) -- if memory is unavailable

  permission-error(file-name) -- no permission to read a file

  A system-error(description) -- internal system error

  type-error(expected,actual) -- data type error

  domain-error(functor,offending-value) -- the offending value is not in the domain of the functor. For instance, in load_structure( string('<m></m>'), Document, [line(xyz)], Warn), xyz is not in the domain of line.

  existence-error(resource) -- resource does not exist

  limit-exceeded(limit,maxval) -- value exceeds the limit.