[Haskell-cafe] If you'd design a Haskell-like language, what would you do different?

[Gregory Crosswhite]

On Dec 20, 2011, at 8:05 PM, Tillmann Rendel wrote:

> Hi,
> 
> Robert Clausecker wrote:
>> Image you would create your own language with a paradigm similar to
>> Haskell or have to chance to change Haskell without the need to keep any
>> compatibility. What stuff would you add to your language, what stuff
>> would you remove and what problems would you solve completely different?
> 
> I would try to improve the language's support for the embedding of domain-specific embedded languages (aka. combinator libraries). Such embedding requires the integration of a domain-specific language's syntax, static semantics and dynamic semantics. Some (more or less far fetched) ideas about these three areas follow.
> 
> 
> To support better syntax for embedded languages, provide more rebindable syntax à la do-notation. For example, (if c then t else e) currently desugars to (case c of False -> e; True -> t). But it could also desugar to (if' c t e) where if' is a method of a type class. For (c : Bool), the standard library would provide an instance of this type class, but for other condition types, third-party libraries could provide it. Alternatively, if-then-else could even desugar to whatever if' is in scope. A similar idea is currently applied to Scala in the scala-virtualized project. A large part of the language should be virtualized this way, including pattern matching, lambda expressions, maybe even type or class declarations.
> 
> To support better static semantics for embedded languages, provide better type-level computation, including some form of closed-world reasoning (for example, backtracking or closed pattern matching) and a reification of names at the type level, so that type-level computations can reason about the binding structures of expressions-level code. Note that I am interested in the static structure of terms, not their dynamic behavior, so this is different from dependent types.
> 
> With Haskell being a fine general-purpose programming language, and even having a good foreign language interface, there is already plenty of support for the specification of dynamic semantics. Nevertheless, for domain-specific embedded compilers, it would possibly be nice to access a Haskell compiler at runtime, to compile snippets of Haskell code and dynamically link them into the currently running program.

So in other words, you would like Haskell to simultaneously become more like Lisp and more like Agda?  :-)

Cheers,
Greg
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