a classy little scripting language

0.4.0 released!

8 April 2021

This post is all about the 0.4.0 release since it’s a big one!
(A separate post for 0.5.0 goals would likely come later.)

0.4.0 details #

0.4.0 contains 145 commits from 28 contributors.

The full release notes link to each PR or commit, and contains a lot more details than this post.

As usual, let’s revisit the goals from the 0.3.0 post.

Most importantly - compound operators didn’t land in 0.4.0 for various reasons. Still working on it, it’s just a fun and nuanced problem and I don’t want to keep 0.4.0 back cos of it.

With that out the way, let’s see what 0.4.0 contains!

0.4.0 highlights #

Below we’ll highlight some key features, fixes and improvements from the release.

A lot of work came from the community, much thanks to everyone contributing!

You can find all the details and the contributions in the release notes.

Take note! There are two minor breaking changes in the API on the release notes.

Bug fixes #

Several important bugs have been fixed, sneaky stack corruptions and some user experience fixes that clarify confusing states.

Documentation #

A lot of work has gone into documentation this release, revising, fixing, adding and closing gaps that were left. For example, Wren supports multi-line strings but this was never mentioned anywhere!

New continue keyword #

Loops can now use continue, which is a welcome addition.

New as keyword #

You can now use import "..." for Name as OtherName to avoid name conflicts, or to use aliases/shorthand for imported variables.

Raw strings #

Wren now supports triple quotes for a string """.

This type of string is only unique in how it’s parsed, the content of the string is ignored (no interpolation or escapes are processed), which allows complex strings to be expressed without needing to escape things.

A common example is json or regex, where there’s a lot of escaping that obscures the string content and makes it hard to read and maintain.

If they span multiple lines, the string ignores the open and closing newlines and whitespace and preserves anything in between.

var json = """
    "hello": "wren",
    "from" : "json"

Attributes #

Attributes are user-defined metadata associated with a class or method that can be used at runtime, by external tools (and potentially by Wren itself).

#hidden = true
#doc = "A simple example class"
class Example {}

They can be:


Below you can one obvious use case, a wip version where attributes for docs were parsed and sent over to vscode to display.

Runtime access
By default, attributes are compiled out and ignored. For an attribute to be visible at runtime, mark it for runtime access using an exclamation:

#doc = "not runtime data"
#!runtimeAccess = true
#!maxIterations = 16

Attributes at runtime are stored on the class itself. You can access them via YourClass.attributes. If any attributes are made available, they’ll be found here:

All the details for Attributes can be found here.

Chained methods fixes (‘fluent interfaces’) #

Mentioned in the last post, you can now use this pattern in code as intended, the same-line requirement for the . has been removed.


List additions #

Lists are now sortable via list.sort() and list.sort {|a, b| ... }. You can find an index of something via list.indexOf(value), and remove a value via list.remove(value). There’s also list.swap(index0, index1) for moving items around within a list.

For the API, wrenSetListElement now exists, and both set and wrenGetListElement now accept negative indices same as the language side.

Num additions #

A few new constants:

And some new methods on a number:

Map access from the API #

You can now create and access maps from the API:

Till next time #