6 kyu
Interpolation Phalanx
130tel
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Interpreters
Fundamentals
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It would be nice if the declaration of
interpwas changed tointerp :: (Name -> Maybe String) -> Phalanx -> Maybe Stringas the current one suggests that it receives a function(Name -> Maybe String)and returns another function(Phalanx -> Maybe String).which is true with and without the parentheses because of Haskell's autocurrying. But I agree that the parentheses should be omitted as they do nothing.
Needs random tests
( Haskell )
needs upgrade to
GHC 8.8.xThat means splitting the
instance Monoidintoinstance Semigroupandinstance Monoid(mappenddoes not seem to be futureproof, so just additionally defininginstance Semigroup where (<>) = mappendis not an optimal solution ) and updating the description, the initial solution and the example solution.( Crikey. That's a lot of work for a kata that doesn't even have random tests. )
Done.
All existing solutions invalidated - they need a split
Monoidinstance as well.Any replies to this thread will generate a notification to me; new posts may not.
I found the intructions somewhat cryptic compared to those in
daggerandrazor, but once I figured out what you wanted it wasn't too bad.This comment has been hidden.
The only issues I've found are in the description: it should mention that you have to implement rep, and maybe be a little nicer on the description of interp. For such an easy kata, I would mention what the first parameter actually is (the dictionary lookup function)
Unclear instruction. You should be more specific about difference between Lookup and Literal
You can recover the meaning from the test cases. It's difficult to describe them without giving away exactly the implementation.
First it wasn't clear to me what the point was in defining
repandl. Maybe some explanation that these are the "constructor functions" which can be used to build upPhalanxcould be useful. Theninterpbreaks down what we have built. I thought that the whole point was to implementinterpand first I wondered why the rest was needed..I'm intentionally a little vague around that. You can read the idea that "
interpbreaks down what we have built" by thinking about the tail end of its type:Phalanx -> String. If you haven't done the razor and dagger language kata yet then they hopefully build that intuition.The other reason I am intentionally a little vague here is because there are two ways to solve the
repbit and if you end up going down one path and then notice the other you'll be forced to consider something really interesting about DSLs/embedded languages likePhalanx: the idea of a basis encoding.Some things are not clear:
Which is correct:
interp e Empty == Nothingorinterp e Empty == Just ""?Is it OK for
repto join an extraEmptyat the end? For example:rep 2 (Literal "A") == Literal "A"
JoinLiteral "A"JoinEmptyEmpty should produce the empty string. Nothing is reserved for actual interpretation failures. Rep can work that way if you like, can you formulate a set of laws about the behavior of
interpwhich prove it?It would be nice to have the typeclass definitions in the code.
Sure, I'll add them as comments.
wheremissing at bothinstancedeclarationsishould belinstead (according to a post below that should have been fixed, but it still appears this way)Thank you, found another location for
i -> l. The missingwhereis valid syntax when the instance definition itself is empty. These instances must be filled in before the test cases will compile.You're right. And thanks for fixing the
iandl.Np! Thanks for pointing out the mistake!
The function called "i" in the text and code should be named "l", since this is what the test expects.
Good call, I missed that on the edit. Fixed now!