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include | ||
src | ||
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editor.html | ||
elm-package.json | ||
elm.js | ||
Main.elm | ||
main.html | ||
README.md |
This is the Elm version of the Unison editor. It is no longer being maintained and will be replaced by a Haskell version, currently in development (see the editor/
) directory.
If you want to run this, you'll need to install Elm 0.15 first. Make sure you have a node running (via a cabal run node
in the node/
subproject shell) as well, since the editor has to talk to the node.
$ cd editor-elm
$ elm make src/Unison/Editor.elm
Some new packages are needed. Here is the upgrade plan.
Install:
elm-lang/core 2.0.1
evancz/elm-http 1.0.0
Do you approve of this plan? (y/n) y
Downloading elm-lang/core
Downloading evancz/elm-http
Packages configured successfully!
Compiled 62 files
Successfully generated elm.js
$ elm reactor
Elm Reactor 0.3.1 (Elm Platform 0.15)
Listening on http://0.0.0.0:8000/
Now open up a browser and go to http://0.0.0.0:8000/
. Navigate to src/Unison/Editor.elm
. You should see the Unison expression editor, initially consisting of a single _
. You can navigate around with the keyboard or mouse. Use <Enter>
or a click to open a node for editing. Some other keyboard commands:
<Enter>
accepts the current selection in the explorer, and arrow keys or the mouse navigate.- When the explorer is closed:
's'
performs linking + 1 beta reduction of the selected expression.'e'
evaluates the selected expression to weak head normal form.'a'
wraps the current selection in a function call, initially blank'v'
switches between the 'raw' and interpreted view
Somewhat annoying---when the explorer pops up, it doesn't get focus. Hit tab once to make the focus active, or click in the text box. You might notice some other minor issues.
If you have the elm reactor running, you can make edits to the code, save, and refresh the page to see them.
A brief code tour
The Elm-based Unison editor is not much code:
$ cd editor-elm
$ find src -name '*.elm' | xargs wc -l
24 src/Elmz/Distance.elm
80 src/Elmz/Json/Decoder.elm
109 src/Elmz/Json/Encoder.elm
50 src/Elmz/Json/Request.elm
292 src/Elmz/Layout.elm
8 src/Elmz/List.elm
54 src/Elmz/Matcher.elm
48 src/Elmz/Maybe.elm
83 src/Elmz/Mealy.elm
107 src/Elmz/Moore.elm
115 src/Elmz/Movement.elm
148 src/Elmz/Parser.elm
8 src/Elmz/Result.elm
76 src/Elmz/Selection1D.elm
211 src/Elmz/Signal.elm
75 src/Elmz/Trie.elm
6 src/Elmz/Void.elm
39 src/Unison/Action.elm
131 src/Unison/EditableTerm.elm
314 src/Unison/Editor.elm
17 src/Unison/Hash.elm
93 src/Unison/Metadata.elm
149 src/Unison/Node.elm
119 src/Unison/Path.elm
43 src/Unison/Reference.elm
98 src/Unison/Scope.elm
87 src/Unison/SearchboxParser.elm
231 src/Unison/Styles.elm
54 src/Unison/Symbol.elm
329 src/Unison/Term.elm
311 src/Unison/TermExplorer.elm
47 src/Unison/Terms.elm
130 src/Unison/Type.elm
380 src/Unison/View.elm
4066 total
Since most of this code will likely be getting a rewrite when moving away Elm, we'll avoid going into too much detail. At a high level:
- The
Elmz
package has various utility modules, not specific to Unison. - The
Unison.Editor
module is the main entry point for the editor. - Many of the modules in the
Unison
package mirror their counterparts in Haskell. The representation of terms and types is a bit different from the Haskell side. Unfortunately, Elm's type system cannot represent abstract binding trees, so the the JSON encoders/decoders in Elm convert both terms and types to and from simpler, more Elm-friendly represenations. - There are a few modules which get used a lot:
Elmz.Layout
, which I'm calling an 'annotated layout tree'. It's a pretty simple idea that lets us use regular pure functions to do hit testing, compute selection highlight regions, and so on. There's a description of the technique and some discussion in this blog post. The editor uses this in lots of places.Elmz.Moore
andElmz.Mealy
are pure state machine types, with the minor twist that they may drop events. Most of the components of the editor UI are defined as someMoore i o
, wherei
will be some type which is the union of all events that component can receive, and whereo
might be a view and some other values to pass along.Moore
andMealy
values can be assembled using various combinators, created with recursion, and fed explicitly. This all works out okay and is pretty simple, but it also requires some manual plumbing.