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Logtalk - Object oriented extension to Prolog
Release 2.21.5

Copyright (c) 1998-2004 Paulo Moura.  All Rights Reserved.
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Upgrading from Logtalk 1.x
==========================

Logtalk 2.x is not compatible with programs written for version 1.x.
However, you should be able to translate most programs to make them 
run under this new version. Most of the examples provided with previous 
versions have been rewritten to run under version 2.x. Use them as 
translation examples.


Upgrading from a previous Logtalk 2.x version
=============================================

If your Logtalk programs depend on some of the example files, it is
advisable that you check your code against the new version before 
throwing away the older release.

Logtalk source files will need to be recompiled because of the changes 
done in the version 2.5.0 to improve message sending performance.

Logtalk version 2.7.0 provides the first cut of the Logtalk standard library.
Most examples have been rewritten to take advantage of the library.

Logtalk version 2.8.0 introduces a small change on the logtalk_compile/1-2 
and logtalk_load/1-2 predicates that may imply updating your loader utility
files: the first argument is now always a list of entities even if we want 
to compile or load a single entity.

Logtalk version 2.9.0 changes compiled code functors postfixes from "_sdcl" 
and "_sdef" to  "_idcl"	and "_idef", implying recompilation of all objects, 
protocols, and categories.

Logtalk version 2.10.0 changes some of the semantics of object dynamic 
predicates. See the release notes for a description of the changes.

Logtalk version 2.14.4 removes the definition of the deprecated built-in 
predicate logtalk_version/3 (use current_logtalk_flag/3 instead).

Logtalk version 2.14.5 changes compiled code in order to correct a bug 
where sending messages such as true/0 to an unknown object will succeeded 
instead of throwing the expected exception, implying recompilation of all 
objects, protocols, and categories.

Logtalk version 2.14.7 changes compiled code in order to optimize the 
code generated by the compilation of dynamic predicate clauses.

Logtalk version 2.15.0 changes the "authors" key in  the directive info/1 to 
"author". All the XSLT, DTD, and XSD files have been update to conform to 
this change. If you use the directive info/1 in your programs, you will need 
to apply this change to take advantage of automatic generation of documenting 
files.

Logtalk version 2.15.3 changes the format of the runtime entity tables, 
implying recompilation of all objects, protocols, and categories.

Logtalk version 2.15.6 renamed the compiler option "named_anonymous_vars" to 
"underscore_vars" and changed the possible option values form "on/off" to 
"dont_care/singletons".

Logtalk 2.16.0 improves support for the declaration and use of operators 
local to objects and categories. Recompilation of any objects and categories 
containing operator declarations is needed in order to take advantage of the 
improvements made.

Logtalk 2.16.1 now checks for attempts to redefined built-in Logtalk control 
constructs when compiling source files. These checks may generate compilation 
errors on files containing bugs that are not detected on previous versions of 
the compiler.

Logtalk version 2.16.2 changed the possible option values of the read-only 
compiler option "startup_message" to "none", "banner", and "flags". Default 
value is "flags" (print both banner and default flag values).

Logtalk version 2.17.1 removes predicate nth/3 from library entities listp, 
list, and difflist (replaced by the predicates nth0/3 and nth1/3).

Logtalk version 2.20.0 updates the semantics of the uses/1 entity directive 
to accept as argument a single object identifier (this change is needed in 
order to ensure compatibility with the new uses/2 predicate directive).

Logtalk version 2.21.2 adds a new clause to the code generated when compiling 
entity in order to support the new alias/1 predicate property, implying 
recompilation of all objects, protocols, and categories.