[Haskell-cafe] Sifflet type checker [from Re: [Haskell] ANNOUNCE: Sifflet visual programming language, release 188.8.131.52]
gdweber at iue.edu
gdweber at iue.edu
Mon Jul 9 18:51:29 CEST 2012
On 2012-Jul-07, Henning Thielemann wrote:
> On Thu, 5 Jul 2012, gdweber at iue.edu wrote:
> >Sifflet and sifflet-lib 184.108.40.206, now available on Hackage!
> >This version introduces a type checker and partial support
> >for higher order functions in Sifflet, the visual, functional
> >programming language and support system for students learning
> >about recursion.
> You have implemented your own type-checker, right?
It is my code implementing the type checker from Simon Peyton-Jones's
book "The Implementation of Functional Programming Languages" (1987).
> I plan to add a
> type-checker to our live-sequencer project.  So far I have
> thought about using the Helium type checker but I have not done it
> so far. If you want to make your type-checker useful for other
> projects, you may put it into a separate package without the hard to
> install dependencies on cairo and glib.
I am very interested in receiving suggestions for modularizing
my packages, and I thank you for this one.
I should point out that the Sifflet type checker (unlike Helium's)
is not a type checker for Haskell, or even a reduced version of Haskell,
but for a very small language consisting of these expressions
data Expr = EUndefined
| ESymbol Symbol
| EBool Bool
| EChar Char
| ENumber Number
| EString String
| EIf Expr Expr Expr -- ^ if test branch1 branch2
| EList [Expr]
| ELambda Symbol Expr
| EApp Expr Expr -- ^ apply function to argument
| ECall Symbol [Expr] -- ^ function name, arglist
| EOp Operator Expr Expr -- ^ binary operator application
| EGroup Expr -- ^ grouping parentheses
deriving (Eq, Show)
(there are some redundant variants there, because I
designed Expr before thinking about type checking and then
augmented it to add the type checker)
and these types
data Type = TypeVar TypeVarName -- named type variable
| TypeCons TypeConsName [Type] -- constructed type
Do you still think my type checker would be useful to you,
or to Haskellers generally?
>  http://www.youtube.com/watch?v=sXywCHR9WwE
Ah, I enjoyed the performance!
Gregory D. Weber, Ph. D. :
Associate Professor of Informatics / \
Indiana University East 0 :
Tel. (765) 973-8420; FAX (765) 973-8550 / \
http://mypage.iu.edu/~gdweber/ 1 
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