The Snap team is happy to announce the release of version 0.13 of the Snap Framework. We would like to thank Edward Kmett who helped with some of the broad design ideas incorporated in this release.

The Heist API changed significantly in this release. If you are migrating an existing app to 0.13, check out the following diffs to see how the migration was done in some real packages.

Major Changes

The API for compiled Heist has now stabilized. The new API is much simpler than the old one. The old API had inconsistent use of n a , RuntimeSplice n a , and Promise a , which made it difficult to understand how things should be composed. Since those three things are different incarnations of roughly the same general idea, we were able to simplify the high-level API to just use RuntimeSplice n a everywhere.

The low level Heist API was moved to its own module. The high-level API referred to above is much simpler, but slightly restricted in its power. If you need to write compiled splices with special control flow, then you will need to import the low level API and work with promises directly.

Heist now has new syntax for writing splices. The old alist syntax made behavior unclear when the same splice name occurred more than once. Also, the actual syntax for alists is not incredibly clean either. The new syntax is defined in the Heist.SpliceAPI module and leverages do notation and a few infix operators to create elegant syntax for defining splices while at the same time making semantics more clear.

The snaplet testing API has been modified to allow you to choose an environment.

Bugfixes / minor improvements