Morrow Download

The Morrow compiler is not nearly complete: it does not generate code yet and the type checker is only partially implemented. Read the introduction to read more about using the Morrow interpreter.

The latest stable version of Morrow can be downloaded with darcs:

> darcs get --partial http://www.equational.org/repos/morrow/main

The latest development version that supports existential types can be downloaded as:

> darcs get --partial http://www.equational.org/repos/morrow/branches/morrow-ex

After downloading, use configure and make to build Morrow. You need to have a recent Haskell compiler (GHC, NHC, or Hugs) and the UUAG attribute grammar system. There is precompiled version of UUAG for windows, just put in it somewhere in your path.

Once downloaded, you can build the system using:

> configure
> make interactive

Use configure --help and make help to get more information about the build process. If you experience download or build problems, or if you would like to have a binary version, you can send an email to the designer.

Currently, the Morrow interpreter compiles and executes expression using OCaml. You need to have ocamlc in your path if you want to run expressions (otherwise, only the inferred types are shown).

Status

Parser and static checks completed.
The type inferencer is partially completed with polymorphic kind inference and higher-rank types
Code generation to OCaml. If ocamlc can be found, it is used to compile and execute expressions.
First-class existential types are supported in the latest development version. There is a draft paper that describes the basic design. Existentials get opened automatically when applied to a function that polymorphic in the existential type. The some quantifier can be used to explicitly open existentials at let bindings. For example.
```
type Key a = { val :: a, key :: a -> Int }

absInt :: exists a. Key a
absInt = { val = 1, key i = i }

one1 = (\x -> x.key x.val) (head [absInt])

one2 = let x :: some a. Key a
           x = absInt
       in x.key x.val
```

"Jul 13 2006"