latitude

The Exception Object and Built-in Exceptions

Exception := Object clone.

An exception is an error condition, usually raised with the throw method. The details of the exception-handling mechanism in Latitude can be found at Exceptions.

Simple Slots

Exception message := "Exception!".
Exception toString := "Exception".
Exception stack := Nil.

Methods

Exception throw.

Throws the current object, triggering any exception handlers that are in scope. Unlike Object throw, this method assigns a stack slot to the curent object, which contains the current stack trace at the time the exception was thrown, as per currentStackTrace.

Exception throwWith (message).

Throws the current object, as though by throw. Before throwing, the exception object’s message slot is set to the throwWith argument.

Exception pretty.

Produces a string represent of the exception which consists of its name (as per toString), followed by a delimiter (usually a dash), followed by the exception’s message (as per message).

Exception printStackTrace.

Prints the stack trace of the exception object. This call is equivalent to self stack dumpObject..

Exceptions

The err singleton object contains several built-in exceptions, which are thrown by standard library functions in the case of failure. Unless otherwise stated, all of the below exceptions are only found in slots on err, not in the global scope. Additionally, each exception listed here has a toString slot which evaluates to its own name and, unless otherwise stated, is a subobject of SystemError.

Exception

The root exception object, which is defined in err in addition to being available as a globally-scoped name.

SystemError

err SystemError message := "System Exception!".

This is the parent object of all exceptions thrown by the standard library. Unlike many of the exceptions available here, it is available as a globally scoped name and within err. SystemError is a direct subobject of Exception.

ArgError

err ArgError message := "Argument error".

This exception is thrown when arguments to a method are invalid and none of the more specific exceptions make sense for the situation.

BoundsError

err BoundsError message := "Bounds error".

This exception is thrown when an invalid index is provided to a container-like structure.

IOError

err IOError message := "IO error".

This exception is thrown if an error occurs while performing an I/O operation.

InputError

err InputError message := "Input error".

This exception is thrown when a string parse is attempted, and the string fails to be recognizable as a valid value of the target type.

IntegrityError

err IntegrityError message := "Integrity error".

This exception is thrown when a string of a specific format is expected, and the string does not satisfy the given format.

UTF8IntegrityError

err UTF8IntegrityError message := "UTF-8 Integrity error".

A subobject of IntegrityError, this exception is thrown if a string which is not a valid UTF-8 string is constructed.

LangError

err LangError message := "Error reading from external language".

This exception is thrown when a language parse (using the #() syntax) is attempted and fails.

ModuleError

err ModuleError message := "Module error".

This exception is thrown when a module load is attempted and fails, usually because a module with the given name cannot be found.

NotSupportedError

err NotSupportedError message := "Not supported".

This exception is thrown when a platform-specific method is invoked and is not supported on the current platform.

ParseError

err ParseError message := "Parse error".

This exception is thrown by the Latitude parser in the case of a syntax error within Latitude code.

ReadOnlyError

err ReadOnlyError message := "Write access prohibited".

This exception is thrown when a write is attempted on data which is intended as read-only, such as attempting to modify the elements of a read-only iterator.

ProtectedError

err ProtectionError message := "Protected variable".

This exception, a subobject of ReadOnlyError, is thrown by the Latitude VM if an operation is attempted which violates the slot protection of a slot.

SlotError

err SlotError slotName := Nil.
err SlotError objectInstance := Nil.

This exception is thrown if a slot which does not exist is accessed on an object. The message slot of this object is a method which returns an appropriate message, containing the slot name.

SystemArgError

err SystemArgError message := "Wrong number of arguments to system call".

As the message name indicates, this exception is thrown when a system-level call is made with incorrect arguments.

TypeError

err TypeError message := "Type error".

This exception is thrown if an object whose type or characteristics are not what are expected is passed to a method.

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