Am Samstag, 2. Februar 2008 14:54 schrieben Sie:
On Feb 1, 2008 10:32 PM, Wolfgang Jeltsch wrote:
Am Freitag, 1. Februar 2008 13:00 schrieb Alfonso Acosta: […]
To make it friendlier for the end user I thought about defining aliases for lets say the first 10000 numbers using Template Haskell. That could even make error reports friendlier (not sure to what point though). What do you think?
I have no clear opinion about that at the moment. Maybe it's okay to use the representation directly. This way, we don't introduce a dependeny on the Template Haskell language extension (which is only supported by GHC), and the actual representation will occur in error messages anyway whenever the message shows a computed number.
Well, my EDSL already makes extensive use of TH. So, being selfish, it wouldn't be a problem for me (or any other GHC user) and I think it would make the library much more usable.
Just compare
f :: List (() :- D1 :- D0 :- D0 :- 1000) Int -> List (() :- D1 :- D0 :- D0 :- D0) Int
with, let's say
f :: List A1000 Int -> List A1000 Int
Again, if someone complains about the TH dependency, the aliases could be generated by TH but saved statically in a module for each release.
Hmm, this could be a compromise although I’m not sure whether it is sensible to have a module with thousands of declarations. Another solution would be to put the Template Haskell convenience stuff into a separate package. The core package would probably be usable with Hugs too, while the convenience package would be usable only with GHC. At the moment, I’m not sure how often I’ll need to state type-level numbers explicitely. So currently I cannot know how important aliases for type-level numbers are.
So, we'll be making two separate libraries then. We should think about names.
What about FixedVector for the vector library and DecTypArith (maybe too long) or DecTypes for the type-level decimal arithmetic library?
Alas, there is an inconsistency in naming packages already. Some prefer names which are entirely lowercase, some prefer camel case. I prefer lowercase, with hyphens separating parts of the name. And I also don't like unusual abbreviations like "typ" (not much shorter than "type"). To mention arithmetics is not so important. So maybe something like "type-level-decimals"?
Maybe it's better to put different type-level programming things into a single package. Then we could name this package "type-level" or something similar. We could start with our decimals. Other type-level things could be added later. I already have some code about type-level booleans. It's not very sensible to put these few lines into a separate package. It might be nice if we had a general type-level programming package where I could put this code into.
Sounds sensible. However, I would rather prefer something like type-level-comp (from type level computations) or type-level-prog (from type level programming). Type level by itself doesn't describe the functionality of the package.
Hmm, package names don’t have to be descriptive. Short names tend to sound better and be easier to remember. My FRP GUI and graphics library is named Grapefruit. This name makes hardly any sense. It refers to the previous library Fruit and the fact that I like Grapefruits—nothing more. But it’s a name, people can remember more easily than FRGGLER (Functional Reactive GUI and Graphics Library with Extensible Records). ;-) In addition, abbreviations like “comp” typically have the problem of being ambiguous: computation, composition, component, … So I still prefer type-level.
As for the name of the fixed-size list package, I have to say that I don't like the term "vector" in this context. A vector is actually something with addition and scalar multiplication defined on it. Maybe we should make also this package's scope wider. What about something like "safe-data" or similar?
I think safe-data is a bit too general and might lead to confusion with other safe data packages (namely Mitchell's Safe library). Since the main particularity of the library is that safety properties are achieved via "emulating" dependent types I think that light-dependent-types (from lightweight dependent types), number-parameterized-data or simply parameterized-data (this is the name I like best) would be more appropiate.
parametrized-data looks good. The others seem to be too long again. So type-level + parametrized-data is my vote. But don’t let’s spend too much time discussing the name. ;-) Best wishes, Wolfgang