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17 May 2006

by Noel

More Dagstuhl Talks


Matthew Flatt

A module is “the way you share code with other programmers”

Module systems in different languages: Python, Ruby

Mutually dependent modules are the first issue

Ruby example: mutually dependent modules sometimes work
(when required from files) but dependent on order of
execution. Shows that a module definition is a
side-effecting operation. Similarly a module may be
extended. Hence a module is a runtime concept.

Ruby modules also function as mixins.

MzScheme modules are not side effects. Runtime order does
not matter. However expand time (aka static analysis time)
order does. Mutually dependencies disallowed. Use units
for mutual dependencies. (New!) Unit/signature modules. A
module can be written in a unit or signature language.
External linking — the module no longer decides what it
links to (cf internal linking, the usual method).

Scheme48 modules, known as structures. Similar to MzScheme
units and ML functors. However allows units to export
macros, unlike MzScheme.

Smalltalk modules


Smalltalk 80 has no modules. Distribute changesets.
Changesets have no composition.

VisualWorks/Squeak packages track their changes and so can
be uninstalled. Packages have prerequisites.

Selector namespaces in Modular Smalltalk. They are not
reentrant. Seems to have strange scoping rules.

Classboxes allow re-entrance.


Mike Sperber

Pragmatics and deployment.

Tools create boilerplate. Standard format for packaging and

Online distribution (CPAN) and shell for retrieval and
installation. Can automatically install dependencies.

Perl code may branch depending on installed modules and

Social features (e.g. number of available modules) make it
difficult to change the implementation. For instance, you
can only have 1 version installed at a time. Cf PLaneT
allows multiple versions. However there are still issues
with loading multiple versions at once.

Java’s Future

Gilad Bracha

JSR-277 attempting to add a module system for Java. Main
interest is deployment, versioning etc.

Initial proposed system: modules are like units –

Actual proposed system: no language changes allowed.
Instead embed using reflective API. Turing complete
therefore any particular implementation possible
(first-class, higher-order, etc.)

Module implementations check for prerequisites at runtime.
Just code, so anything is allowed. Lots of state.

My comments: As usual for Java has taken a
reasonable idea and turned it into a huge hairball.

Soapbox Session

Context-oriented Programming

Pascal Constanza

Make program change behaviour due to context of use
(e.g. personalisation) without making it a huge hairball.

Basically a new type of modularity. Similar to aspects, and
OO inheritance / overriding.


Philippe Mougin

Open source scripting language for Cocoa / OS X

Unifies OO and array programming

Interactive environment.

Source Code Mining for Latently-Typed Languages
Dave Mandelin

Extracting information from source code. Perhaps to find
out how to use a library from example code.

Example: what are the types of the arguments in a latently
typed language?



Trygve Reenskaug

Modularity, again.

My comments: I didn’t really get this talk, so my summary is brief and perhaps incorrect.

Ambient Oriented Programming

Ambient resources and volatile connections

Non-blocking communication

Reified communication traces

Reified environmental context

OO sans classes to handle code updates


Laurence Tratt

Pythonic language with compile time metaprogramming ala
Template Haskell.

Converge’s role is to host DSLs, and so must be very
flexible. In a senese a Lisp with curly braces.

Customisable parsing.

Father Time

Greg Cooper


Guillaume Marceau

My comments: I’ve seen FrTime and MzTake before
so I didn’t take notes. If they’re new to you check them
out — they come as part of PLT Scheme

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