Fix the implementation of Let #1

New Issue

2016-08-05T10:55:17+01:00

SuzanneSoy commented

2016-08-05 10:55:17 +01:00

(Migrated from github.com)

Allow more complex types than just identifiers in the type expressions which get bound
Fix hygiene problems (read Matthew Flatt's Binding as Sets of Scopes for details on how to do this)
implement Let* (trivial, I think the current implementation of Let actually behaves like Let* should) and Let-rec
implement some kind of syntax-local-type-introduce

(Let ([v e] …) t)

The Let form binds each type expression
e (which may contain uses of type expanders bound
outside of the Let) to the identifier v.
The type t can contain type expanders and can
refer to occurrences of the bound v identifiers,
which expand to e. The Let form therefore
behaves is a way similar to let-syntax.

The current implementation is extremely limited: it only
supports type identifiers for the e type
expressions, and most likely does not work in a hygienic
way. It would also be better to define Let,
Let* and Let-rec, as well as some kind
of syntax-local-type-introduce.

- Allow more complex types than just identifiers in the type expressions which get bound - Fix hygiene problems (read Matthew Flatt's [Binding as Sets of Scopes](http://www.cs.utah.edu/plt/scope-sets/) for details on how to do this) - implement `Let*` (trivial, I think the current implementation of `Let` actually behaves like `Let*` should) and `Let-rec` - implement some kind of `syntax-local-type-introduce` ``` racket (Let ([v e] …) t) ``` The `Let` form binds each type expression `e` (which may contain uses of type expanders bound outside of the `Let`) to the identifier `v`. The type `t` can contain type expanders and can refer to occurrences of the bound `v` identifiers, which expand to `e`. The `Let` form therefore behaves is a way similar to `let-syntax`. The current implementation is extremely limited: it only supports type identifiers for the `e` type expressions, and most likely does not work in a hygienic way. It would also be better to define `Let`, `Let*` and `Let-rec`, as well as some kind of `syntax-local-type-introduce`.

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