3. a technique for modeling a GUI as a declarative state machine
PureScript only competes with #1 and #2 here. Where Elm really shines is #3, which #2 helps with a lot.
Technically #3 could be done in any language. But it really helps to model it in such an expressive language with immutable data and no side-effects (except via Signals).
1. an language very similar to Haskell
2. a set of runtime libraries
3. a technique for modeling a GUI as a declarative state machine
PureScript only competes with #1 and #2 here. Where Elm really shines is #3, which #2 helps with a lot.
Technically #3 could be done in any language. But it really helps to model it in such an expressive language with immutable data and no side-effects (except via Signals).