Wearing the hair shirt Wearing the hair shirt - Microsoft Research
Wearing the hair shirt Wearing the hair shirt - Microsoft Research Wearing the hair shirt Wearing the hair shirt - Microsoft Research
Type-based dispatch class Num a where (+) :: a -> a -> a negate :: a -> a fromInteger :: Integer -> a ... double :: Num a => a -> a double x = 2*x means double :: Num a -> a -> a double d x = mul d (fromInteger d 2) x The overloaded value is returned by fromInteger, not passed to it. It is the dictionary (and type) that are passed as argument to fromInteger
Type-based dispatch So the links to intensional polymorphism are much closer than the links to OOP. The dictionary is like a proxy for the (interesting aspects of) the type argument of a polymorphic function. f :: forall a. a -> Int f t (x::t) = ...typecase t... f :: forall a. C a => a -> Int f x = ...(call method of C)... Intensional polymorphism Haskell C.f. Crary et al λR (ICFP98), Baars et al (ICFP02)
- Page 1 and 2: Wearing the hair shirt A retrospect
- Page 3 and 4: Haskell is 15 years old (born FPCA
- Page 5 and 6: Timeline Sept 87: kick off Apr 90:
- Page 7 and 8: Reflections on the process The i
- Page 9: Reflections on process Self-appoin
- Page 12 and 13: Syntactic redundancy Seductive ide
- Page 14 and 15: “Expression style” Define a fun
- Page 16 and 17: Example (ICFP02 prog comp) Pattern
- Page 18 and 19: What really matters?
- Page 20 and 21: But... Laziness makes it much, muc
- Page 22: Combinator libraries Recursive valu
- Page 25 and 26: Monadic I/O A value of type (IO t)
- Page 27 and 28: Connecting I/O operations (>>=) ::
- Page 29 and 30: Control structures Values of type (
- Page 31 and 32: Monads Exceptions type Exn a = E
- Page 33 and 34: The IO monad The IO monad allows
- Page 35 and 36: What have we achieved? ...without
- Page 37 and 38: Open challenge 1 Open problem: the
- Page 39 and 40: Monad summary Monads are a beautif
- Page 41 and 42: What really matters? Laziness Purit
- Page 44 and 45: Type classes class Eq a where (==)
- Page 46 and 47: Type classes over time Type classe
- Page 48 and 49: Quickcheck propRev :: [Int] -> Bool
- Page 50 and 51: Extensiblity Like OOP, one can add
- Page 54 and 55: Cool generalisations Multi-paramet
- Page 56: Type classes summary A much more f
- Page 59 and 60: Is sexy good? Yes! Well typed prog
- Page 61 and 62: Destination = F w
- Page 63 and 64: Modules Porsche High power, but poo
- Page 65 and 66: Encapsulating it all data ST s a --
- Page 67 and 68: Shirts off to Wadler Type classes
Type-based dispatch<br />
So <strong>the</strong> links to intensional polymorphism<br />
are much closer than <strong>the</strong> links to OOP.<br />
The dictionary is like a proxy for <strong>the</strong><br />
(interesting aspects of) <strong>the</strong> type argument<br />
of a polymorphic function.<br />
f :: forall a. a -> Int<br />
f t (x::t) = ...typecase t...<br />
f :: forall a. C a => a -> Int<br />
f x = ...(call method of C)...<br />
Intensional<br />
polymorphism<br />
Haskell<br />
C.f. Crary et al λR (ICFP98), Baars et al (ICFP02)
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