From: hense@sol.cs.uni-sb.de (Andreas Hense) Subject: *** NEW O'small compiler available by ftp !!! *** Date: 25 Jun 1993 13:54:35 GMT Organization: Universitaet des Saarlandes,Rechenzentrum
O'small - THE object-oriented language for teaching
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(Announcement of a new compiler)
*** An object-oriented language for teaching?
Depending on which aspects of object-orientation you want to convey you may choose your teaching language. If you want to teach the aspect of software reuse and nice graphical user interfaces, you should choose Smalltalk. If you want to show students how to program in a best selling language you should choose C++.
*** In which case should I choose O'small?
You should consider O'small if you believe that computer languages should have a GOOD FORMAL SEMANTICS. Everyone will agree that a language needs a formal semantics. Otherwise, your program will yield different results on different implementations. A good formal semantics does not only serve the purpose of precisely defining what the results of your programs are, it also gives insights about the nature of the language.
You should consider O'small if you do not want to waste time on unnecessary details. O'small is CONCISE. Its syntax and semantics takes no more than one page (if you choose the right font). Its syntax is similar to more traditional languages. O'small has been used in a lecture showing the differences between wrapper semantics (denotational) and method lookup semantics (operational).
O'small is FREE! Up to now, there has only been an O'small interpreter written in Miranda [Hen91b]. This interpreter is directly based on the denotational semantics of O'small [Hen91d]. The interpreter itself is available by ftp. However, you need Miranda in order to run it. Now, there is a NEW IMPLEMENTATION of O'small based entirely on EASILY AVAILABLE SOFTWARE. This software is not free but it does not cost anything. The new implementation is based on an abstract machine [Boe93].
You can MODIFY the language and have your students make experiments with it. The source code of the abstract machine and the specifications for the parser and scanner generators are available. Using these generators you can make experiments for your own research in statical analysis of object-oriented languages.
*** I would like to TRY O'small
You get the implementation by anonymous internet ftp. The following table gives the ftp connection information.
Host: Net Address: Directory: ------------------------------------------------------------- cs.uni-sb.de 134.96.7.254 /pub/osmall/machine
The directory /pub/osmall/machine contains the files
README
ANNOUNCE this file
HowToGetML
oma.1.00.tar.Z compressed tar-file
*************************************************************************** NOTE: Ftp should be put into binary mode before transferring the compressed tar file. ***************************************************************************
Here is a sample dialog:
ftp ftp> open cs.uni-sb.de Name: anonymous Password: <your name> ftp> binary ftp> cd /pub/osmall/machine ftp> get README ftp> get ANNOUNCE ( ftp> get HowToGetML ) ftp> get oma.1.00.tar.Z ftp> close ftp> quit
If you have a Sun 4 or a SPARC you can use the existing executable files. Otherwise, you need 'sml-yacc', 'sml-lex' and 'sml-noshare'. Read 'HowToGetML' to obtain them.
Instructions on using the machine are contained in the file README.
References
[Boe93] Christoph Boeschen. Christmas - An abstract machine for
O'small. Master's thesis, Universit"at des Saarlandes,
Fachbereich 14, June 1993.
[Hen91b] Andreas V. Hense. An O'small interpreter based on denotational
semantics. Technical Report A 07/91, Universit"at des Saarlandes,
Fachbereich 14, November 1991.
[Hen91c] Andreas V. Hense. Type inference for O'small. Technical Report A
06/91, Universit"at des Saarlandes, Fachbereich 14, October 1991.
[Hen91d] Andreas V. Hense. Wrapper semantics of an object-oriented pro-
gramming language with state. In T. Ito and A. R. Meyer, editors,
Theoretical Aspects of Computer Software, volume 526 of Lecture No-
tes in Computer Science, pages 548-568. Springer-Verlag, September
1991.
[Hen93] Andreas V. Hense. Denotational semantics of an object-oriented
programming language with explicit wrappers. Formal Aspects of
Computing, 5(3), 1993. to appear.
[HS92] Andreas V. Hense and Gert Smolka. A verification of extensible
record types. In Zhongzhi Shi, editor, Proceedings of the IFIP
TC12/WG12.3 International Workshop on Automated Reasoning,
pages 137-164, Beijing, P.R. China, 13-16 July 1992. Internatio-
nal Federation for Information Processing, Elsevier, North-Holland,
Excerpta Medica.
[HS93] Andreas V. Hense and Gert Smolka. Principal types for object-
oriented languages. Technical Report A 02/93, Universit"at des Saar-
landes, Fachbereich 14, June 1993.
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