# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1386522272 -3600
# Node ID 54289e78af86253ac5d3a0364ac9881d66be9525
# Parent  5d8bc0f435248e148c4de530b2fb826320563a16
Moved the exceptions document into the low-level concepts document.

diff -r 5d8bc0f43524 -r 54289e78af86 docs/exceptions.txt
--- a/docs/exceptions.txt	Sun Dec 08 18:00:53 2013 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,52 +0,0 @@
-Exception Handling
-==================
-
-Active Exceptions
-=================
-
-When an exception is raised, an exception instance is defined as the active
-exception. This active exception remains in force until either a new exception
-is raised in any handling of the exception, or upon exit of a handler where
-the active exception has been caught (thus resetting the active exception).
-
-NOTE: Currently, if classes are used with "raise" statements, no instantiation
-NOTE: of such classes occurs. This should be remedied.
-
-Instructions
-------------
-
-StoreException records the current value reference using the exception
-register.
-
-LoadException obtains the current exception and puts it in the value register.
-
-CheckException checks the current exception against a class referenced by the
-current value.
-
-ClearException resets the exception register.
-
-Handlers
-========
-
-An exception handler stack is defined such that when a try...except or
-try...finally block is entered, a new handler is defined.
-
-When an exception is raised, the program jumps to the most recently defined
-handler. Inside the handler, the stack entry for the handler will be removed.
-
-Depending on the nature of the handler and whether the exception is handled,
-the program may jump to the next most recent handler, and so on.
-
-If no handler is defined when an exception is raised or re-raised, the program
-should terminate. This might be done by having a "handler #0" which explicitly
-terminates the program.
-
-Instructions
-------------
-
-PushHandler(block) defines an active handler at the location indicated by the
-given block.
-
-PopHandler(n) removes the n topmost active handlers. A single handler is
-typically removed when leaving a try block, but potentially more handlers are
-removed when such a block is exited using a return statement.
diff -r 5d8bc0f43524 -r 54289e78af86 docs/lowlevel.txt
--- a/docs/lowlevel.txt	Sun Dec 08 18:00:53 2013 +0100
+++ b/docs/lowlevel.txt	Sun Dec 08 18:04:32 2013 +0100
@@ -11,6 +11,7 @@
  * Instantiation
  * List and tuple representations
  * Instruction evaluation model
+ * Exception handling
 
 Objects and Structures 
 ======================
@@ -363,3 +364,51 @@
 Using the approach where arguments are treated like attributes in some kind of
 structure, we could choose to allocate frames in places other than a stack.
 This would produce something somewhat similar to a plain tuple object.
+
+Exception Handling
+==================
+
+Active Exceptions
+-----------------
+
+When an exception is raised, an exception instance is defined as the active
+exception. This active exception remains in force until either a new exception
+is raised in any handling of the exception, or upon exit of a handler where
+the active exception has been caught (thus resetting the active exception).
+
+The following operations can be employed to achieve this:
+
+StoreException records the current value reference using the exception
+register.
+
+LoadException obtains the current exception and puts it in the value register.
+
+CheckException checks the current exception against a class referenced by the
+current value.
+
+ClearException resets the exception register.
+
+Handlers
+--------
+
+An exception handler stack is defined such that when a try...except or
+try...finally block is entered, a new handler is defined.
+
+When an exception is raised, the program jumps to the most recently defined
+handler. Inside the handler, the stack entry for the handler will be removed.
+
+Depending on the nature of the handler and whether the exception is handled,
+the program may jump to the next most recent handler, and so on.
+
+If no handler is defined when an exception is raised or re-raised, the program
+should terminate. This might be done by having a "handler #0" which explicitly
+terminates the program.
+
+The following operations can be employed to achieve this:
+
+PushHandler(block) defines an active handler at the location indicated by the
+given block.
+
+PopHandler(n) removes the n topmost active handlers. A single handler is
+typically removed when leaving a try block, but potentially more handlers are
+removed when such a block is exited using a return statement.