[Haskell-cafe] I wrote a type checker: ARF. Is it novel?
davidfstr at gmail.com
Wed Sep 9 03:15:50 UTC 2015
> On 07.09.2015 05:21, David Foster wrote:
>> I've written a small untyped language calculus (ARF) [...]
On 9/8/15, 5:42 AM, Andreas Abel wrote:> Why not use one of the 40-year
old type checking algorithms?
I was aware of the Hindley-Milner type system but judged it to not be an
appropriate fit for my ultimate application, namely superimposing a
static type system on top of Python's runtime type system in order to
give it optional static typing.
The type system I have is a flow-based type system, similar to that used
by David Pearce's Whiley language. I have extended his approach to
interprocedural analysis, since I didn't want to require the programmer
to insert any annotations in the original source code, which would be
required by Pearce's original formulation.
> What type do you infer for
> def id(n):
> return n
If the program calls id() with (n = int) in at least one place, with (n
= bool) in at least one place, and with no other argument types
elsewhere, the type of id() will be inferred as:
* id(int) -> int
* id(bool) -> bool
You'll notice no parameterized type was introduced. The ARF type checker
deals with simple non-parameterized types only.
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