Exceptions as Objects - Revision history

Manus at 12:17, 21 January 2016

2016-01-21T12:17:41Z

Manus at 12:16, 21 January 2016

2016-01-21T12:16:43Z

Conaclos: Syntax update 2

2014-07-02T21:59:03Z

Syntax update 2

Conaclos: Style update

2014-07-02T21:58:13Z

Style update

Conaclos: Update syntax

2014-07-02T21:47:36Z

Update syntax

Ted: /* Exception at rescue clause */

2009-03-26T06:24:10Z

‎Exception at rescue clause

Ted: /* Class EXCEPTION */

2009-03-09T01:27:58Z

‎Class EXCEPTION

Ted: Added new section `origin' VS `cause'.

2009-03-09T01:22:18Z

Added new section `origin' VS `cause'.

Ted: Cosmetics

2009-03-09T01:12:21Z

Cosmetics

Manus: /* Exception at rescue clause */

2007-10-08T17:42:19Z

‎Exception at rescue clause

@@ Line 1: / Line 1: @@
 [[Category:Exception]]
-[[Category:Language]]
+[[Category:Eiffel Language]]
 == Overview ==
 This article describes many aspects of Exceptions as Objects (ECMA-367 8.26) which will be implemented in ISE Eiffel. All exceptions will be raised as objects which can be accessed by `last_exception'. Exceptions as objects are known as type EXCEPTION and its descendants. EXCEPTION_MANAGER is introduced to handle common exception class operations, i.e. catch, and ignore.

@@ Line 1: / Line 1: @@
 [[Category:Exception]]
 == Overview ==
 This article describes many aspects of Exceptions as Objects (ECMA-367 8.26) which will be implemented in ISE Eiffel. All exceptions will be raised as objects which can be accessed by `last_exception'. Exceptions as objects are known as type EXCEPTION and its descendants. EXCEPTION_MANAGER is introduced to handle common exception class operations, i.e. catch, and ignore.

@@ Line 294: / Line 294: @@
 class ANY
 ...
-     default_rescue is
+     default_rescue
         do
         end

@@ Line 303: / Line 303: @@
 == Sample code: Raising and catching developer exception ==
 <eiffel>
-    class
+class
-        MY_EXCEPTION
+    MY_EXCEPTION
-    inherit
+inherit
-        DEVELOPER_EXCEPTION
+    DEVELOPER_EXCEPTION
-    end
+end
 </eiffel>
 <eiffel>
-    class
+class
-−
+    A
-    feature
+feature
-        f is
-            local
+        local
-                retried: BOOLEAN
+            retried: BOOLEAN
-            do
+        do
-                if not retried then
+            if not retried then
-                    my_exception.raise   -- Raise user-defined exception.
+                my_exception.raise   -- Raise user-defined exception.
-                end
-            rescue
-                if last_exception = my_exception then   -- Check the exception object was the one user defined.
-                    print ("True" + "%N")
-                else
-                    print ("False" + "%N")
-                end
              end
+         rescue
-         my_exception: MY_EXCEPTION is
+            if last_exception = my_exception then   -- Check the exception object was the one user defined.
-             once
+                print ("True" + "%N")
-                 create Result
+             else
              end
      end
 </eiffel>
 <eiffel>
-    class
+class
-        APPLICATION
+    APPLICATION
-    inherit
+inherit
-−
+    A
-    create
+create
-        make
+    make
-    feature -- Initialization
+feature -- Initialization
-        make is
+    make
-                -- Run application.
+            -- Run application.
-            local
+        local
-                a: A
+            a: A
-                retried: BOOLEAN
+            retried: BOOLEAN
-            do
+        do
-                if not retried then
+            if not retried then
-                    create a
+                create a
-                    a.f
+                a.f
-                end
+            end
-            rescue
+        rescue
-                retried := True
+            retried := True
-                -- `last_exception' is an object of ROUTINE_FAILURE?
+            -- `last_exception' is an object of ROUTINE_FAILURE?
-                if attached {ROUTINE_FAILURE} (create {EXCEPTION_MANAGER}).last_exception as l_exception then
+            if attached {ROUTINE_FAILURE} (create {EXCEPTION_MANAGER}).last_exception as l_exception then
-                    print ("True" + "%N")
+                print ("True" + "%N")
-                else
+            else
-                    print ("False" + "%N")
+                print ("False" + "%N")
-                end
+            end
-                -- `original' exception is the one caused `last_exception'?
+            -- `original' exception is the one caused `last_exception'?
-                if last_exception.original = my_exception then
+            if last_exception.original = my_exception then
-                    print ("True" + "%N")
+                print ("True" + "%N")
-                else
+            else
-                    print ("False" + "%N")
+                print ("False" + "%N")
-                end
-                retry
              end
-    end -- class APPLICATION
+end -- class APPLICATION
 </eiffel>

@@ Line 355: / Line 355: @@
              local
                  a: A
                  retried: BOOLEAN
              do
@@ Line 364: / Line 363: @@
              rescue
                  retried := True
-                 l_exception ?= (create {EXCEPTION_MANAGER}).last_exception   -- Check `last_exception' is an object of ROUTINE_FAILURE
-                 if l_exception /= Void then
+                -- `last_exception' is an object of ROUTINE_FAILURE?
                      print ("True" + "%N")
                  else
                      print ("False" + "%N")
                  end
-                 if last_exception.original = my_exception then   -- `original' exception is the one caused `last_exception'
                      print ("True" + "%N")
                  else

@@ Line 115: / Line 115: @@
 [[Image:exception_in_rescue.png]]
-Exception e2 is thrown away at c.f3, instruction of rescue clause, in which e3 is raised. In this case we only keep e3 in the stack and accessible by `last_exception'.
+Exception e2 is kept as `cause' at d.f4 in which e3 is raised, and being called in rescue clause r2. In this case e3 is accessible by `last_exception' and e2 is accessible by `cause' of e3.
 <br>
 <br>

@@ Line 176: / Line 176: @@
 			-- Code of the exception.
 			-- |Maybe we don't need this anymore
 	exception_trace: STRING_8
@@ Line 191: / Line 188: @@
 	original: EXCEPTION
 			-- Original exception that triggered current exception
 	recipient_name: STRING_8
@@ Line 226: / Line 226: @@
 		require
 			is_raisable: is_raisable
 end -- class EXCEPTION

@@ Line 101: / Line 101: @@
 set_is_ignored (a_exception: TYPE [EXCEPTION]; a_ignored: BOOLEAN)
 </eiffel>
 == Exception at rescue clause ==

@@ Line 86: / Line 86: @@
 <eiffel>
-  is_ignored: BOOLEAN
+is_ignored: BOOLEAN
-  is_caught: BOOLEAN
+is_caught: BOOLEAN
-  is_ignorable: BOOLEAN
+is_ignorable: BOOLEAN
 </eiffel>
@@ Line 94: / Line 94: @@
 <eiffel>
-  is_caught (a_exception: TYPE [EXCEPTION]): BOOLEAN
+is_caught (a_exception: TYPE [EXCEPTION]): BOOLEAN
-  is_ignored (a_exception: TYPE [EXCEPTION]): BOOLEAN
+is_ignored (a_exception: TYPE [EXCEPTION]): BOOLEAN
-  is_ignorable (a_exception: TYPE [EXCEPTION]): BOOLEAN
+is_ignorable (a_exception: TYPE [EXCEPTION]): BOOLEAN
-  catch (a_exception: TYPE [EXCEPTION])
+catch (a_exception: TYPE [EXCEPTION])
-  ignore (a_exception: TYPE [EXCEPTION])
+ignore (a_exception: TYPE [EXCEPTION])
-  set_is_ignored (a_exception: TYPE [EXCEPTION]; a_ignored: BOOLEAN)
+set_is_ignored (a_exception: TYPE [EXCEPTION]; a_ignored: BOOLEAN)
 </eiffel>

@@ Line 111: / Line 111: @@
 <br>
 <b>
-An behavior should be clarified, that when an exception occurs deep in execution level of a rescue clause, `last_exception' is understood as "last unhandled exception".
+A behavior should be clarified, that when an exception occurs deep in execution level of a rescue clause, `last_exception' is understood as "last unhandled exception".
 </b>
 <br>