traps any condition that a more specific condition trap does not trap. For example, if NOVALUE is raised and there is no NOVALUE trap enabled, but there is a SIGNAL ON ANY trap, the ANY trap is called for the NOVALUE condition. For example, a CALL ON ANY trap is ignored if NOVALUE is raised because CALL ON NOVALUE is not allowed.

raised if a command indicates an error condition upon return. It is also raised if any command indicates failure and none of the following is active:

• CALL ON FAILURE

• SIGNAL ON FAILURE

• CALL ON ANY

• SIGNAL ON ANY

raised if a command indicates a failure condition upon return. The condition is raised at the end of the clause that called the command but is ignored if the FAILURE condition trap is already in the delayed state.

An attempt to enter a command to an unknown subcommand environment also raises a FAILURE condition.

raised if an external attempt is made to interrupt and end execution of the program. The condition is usually raised at the end of the clause that was processed when the external interruption occurred. When a Rexx program is running in a full-screen or command prompt session, the Ctrl+Break key combination raises the halt condition. However, if Ctrl+Break is pressed while a command or non-Rexx external function is processing, the command or function ends.

Notes:

1. Application programs that use the Rexx language processor might use the RXHALT exit or the RexxStart programming interface to halt the execution of a Rexx macro. (See the Open Object Rexx: Programming Guide for details about exits.)

2. Only SIGNAL ON HALT or CALL ON HALT can trap error 4, described in Appendix C. Error Numbers and Messages.

raised if a number used in an arithmetic operation has more digits than the current setting of NUMERIC DIGITS. Leading zeros are not counted in this comparison. You can specify the LOSTDIGITS condition only for SIGNAL ON.

raised if an object receives a message for which it has no method defined, and the object does not have an UNKNOWN method. You can specify the NOMETHOD condition only for SIGNAL ON.

raised when the language processor requires a string value from an object and the object does not directly provide a string value. See Required String Values for more information. You can specify the NOSTRING condition only for SIGNAL ON.

raised if an error occurs during an input or output operation. See Errors during Input and Output. This condition is ignored if the NOTREADY condition trap is already in the delayed state.

raised if an uninitialized variable is used as:

• A term in an expression

• The name following the VAR subkeyword of a PARSE instruction

• A variable reference in a parsing template, an EXPOSE instruction, a PROCEDURE instruction, or a DROP instruction

• A method selection override specifier in a message term

/* The following does not raise NOVALUE. */
signal on novalue
a.=0
say a.z
say "NOVALUE is not raised."
exit

novalue:
say "NOVALUE is raised."

raised if any language-processing error is detected while the program is running. This includes all kinds of processing errors:

• True syntax errors

• "Run-time" errors (such as attempting an arithmetic operation on nonnumeric terms)

• Syntax errors propagated from higher call or method invocation levels

• Untrapped HALT conditions

• Untrapped NOMETHOD conditions

Notes:

1. SIGNAL ON SYNTAX cannot trap the errors 3 and 5.

2. SIGNAL ON SYNTAX can trap the errors 6 and 30 only if they occur during the execution of an INTERPRET instruction.

For information on these errors, refer to Error Numbers and Messages.

raised if a condition specified on the USER option of CALL ON or SIGNAL ON occurs. USER conditions are raised by a RAISE instruction that specifies a USER option with the same usercondition name. The specified usercondition can be any symbol, including those specified as possible values for condition.