Topic: Tirade

Recently there were a range of threads on the pharo-dev mailinglist discussing the textual format to use for Smalltalk source code metadata. The discussion veered off from the specific use case but basically four different formats were discussed and compared, of which one I am the author. And oh, sorry for the formatting of this article - I need to change theme on this blog for better readability.

Two years ago I ended up creating Tirade - a new “file format” for Smalltalkers. Or rather, a way to serialize stuff into a sequence of Smalltalk messages with literals as arguments. I have written a few blog articles about Tirade so I will not go into details in this one.

Last night I started hooking Tirade into Deltas. Quick background: Deltas is “Changesets for the 21st century”, or in other words an intelligent patch system under development for Squeak. Tirade is a Smalltalk/Squeak centric “JSON”-kinda-thingy. I made Tirade in order to get a nice file format for Deltas. Just wanted to share how the first trivial code looks, and thus illustrate simple use of Tirade.

In an article recently I described Tirade - a new generic “file format” for Smalltalk/Squeak, or actually a sub language! Since that article I have refined Tirade a bit. Tirade consists today of 4 classes (parser, reader, writer, recorder) totalling about 500 lines of code, excluding tests. Tests are green in 3.10.2, pharo-10231, 3.9, 3.8 and 3.7. It does turn red in 3.6 due to old initialize behavior, some missing methods etc, probably easily fixed if anyone cares. There are no dependencies on other packages. Compared to using the old Compiler»evaluate: it is about 5-7 times faster.

In my revived work on Deltastreams in Squeak I ended up facing the choice of native file format for Deltas. Matthew has made an advanced format called InterleavedChangeset which manages to squeeze a binary representation of a Delta into a Changeset file (which is in Smalltalk chunk format). An impressive feat, and it has the advantage of being backwards compatible in the sense that a Delta in this format can be filed in as a plain old Changeset into an old Squeak image.