VisualAge Generator to Enterprise Generation Language Migration Guide
Even though the syntax of the two languages differs greatly, the VAGen
language can, for the most part, be migrated to the EGL language while
preserving the same behavior as the original VAGen program. However,
there are number of situations in which the EGL syntax is more precise or more
restrictive than in VisualAge Generator. These situations are rare in
typical programs.
However, when they do occur, the migration tool requires cross-part migration
to determine the exact EGL syntax that preserves the behavior you required in
VisualAge Generator. Cross-part migration means that the migration tool
needs to have one or more other referenced parts available to be able to do a
correct migration of the current part. The following are some
examples:
-
In VisualAge Generator you use the DISPLAY I/O option for both display (text)
and printer maps. EGL provides the display statement for text forms and
the print statement for print forms. To facilitate migration from
VisualAge Generator, there is an EGL preference to indicate that you want
VisualAge Generator Compatibility. The VisualAge Generator
Compatibility preference permits the use of the display statement for print
forms. During migration, if the program, its map group, and the map are
all available, then the migration tool can determine whether to migrate to a
display or print statement. However, if the DISPLAY function is being
migrated without a program, then the migration tool cannot definitively
determine whether to use an EGL display or print statement. In this
situation, the migration tool uses the display statement because it is
tolerated for print forms in VisualAge Generator Compatibility mode.
- In VisualAge Generator you use the SET map PAGE statement for both display
(text) and printer maps.
This causes the screen to be cleared if the next CONVERSE or DISPLAY is for a
display map and a page eject if the next DISPLAY is for a printer map.
EGL provides the clearScreen system library function for text forms and the
pageEject system library function for print forms. The VisualAge
Generator Compatibility preference does not affect the use of clearScreen or
pageEject. During migration, if the program, its map group, and the map
are all available, then the migration tool can determine whether to migrate to
the clearScreen or pageEject system library function. However, if the
SET map PAGE statement is used in a function that is being migrated without a
program, then the migration tool cannot definitively determine whether to use
the clearScreen or pageEject system library function. In this
situation, the migration tool uses EZE_SETPAGE, which is intentionally invalid
EGL syntax. This results in an error on the Tasks list so that you are
aware you need to correct the function.
-
In VisualAge Generator, you can specify either an edit table or an edit
function as the edit routine for a map variable field. You cannot
specify both. In EGL, you can specify both the validatorTable and the
validator properties. If the edit table or the edit function is
available during migration, the migration tool can determine whether to set
the validatorTable or the validator property. However, if the part
specified by the edit routine is not available, the migration tool cannot
definitively determine whether to set the EGL validatorTable or validator
property. In this situation, the migration tool attempts to determine
whether the edit routine is a table or function by using information such as
the length of the edit routine name and the existence of an edit
message. If the migration tool still cannot make a determination, it
uses the validator property. There will only be an error on the Tasks
list if the validator is not a function or cannot be found.
The migration tool uses all the available parts in the migration set to
resolve ambiguous situations. To minimize these ambiguous situations,
always include associated parts when you migrate. For example, when you
migrate a program, be sure to include all the parts that you need to generate
the program in VAGen. This ensures the best possible migration of your
parts. For an overview of how the migration tool resolves ambiguous
situations, see the following sections:
See the chapter Handling ambiguous situations for a complete list of the situations where the migration tool
must do cross-part migration to achieve a correct migration and the steps the
migration tool takes to try to make an intelligent choice if the additional
parts are not available.
[ Top of Page | Previous Page | Next Page | Table of Contents | Index ]
(C) Copyright IBM Corporation 1992, 2005. All Rights Reserved.