Section 10.2 - Declaring Exceptions

  Singularity : exception;

To be complete, here's the syntax for defining an exception, describing using BNF:

  exception_declaration ::= defining_identifier_list ": exception;"
  defining_identifier_list ::= identifier { "," identifier }

Exception declarations are generally placed in a package declaration.

Raising an exception is easy, too - just use the raise statement. A raise statement is simply the keyword "raise" followed by the name of the exception. For example, to raise the "Singularity" exception defined above, just say:

  raise Singularity;

The syntax in BNF is:

  raise_statement ::= "raise" [ exception_name ] ";"

You'll notice that the exception_name is optional; we'll discuss what that means in the next section.

Quiz:

Which of the following would define an exception named No_Safety_Net?

1. No_Safety_Net : exception;
2. Exception : No_Safety_Net;

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