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--- pp:2024:l11 [2024/05/20 00:07]
tpruteanu
+++ pp:2024:l11 [2025/05/09 20:59] (current)
ldaniel fix typo at fmap definition
@@ Line 66: / Line 66: @@
 <code haskell>
 instance Functor Foo where
-  fmap f fx = px >>= (\x -> return (f x))
+  fmap f fx = fx >>= (\x -> return (f x))
 instance Applicative Foo where
@@ Line 208: / Line 208: @@
 <code haskell>
-newtype Prob = Prob [(a, Float)] deriving Show
+newtype Prob a = Prob [(a, Float)] deriving Show
 </code>
@@ Line 253: / Line 253: @@
 coin :: Prob Coin
-coin = [(Heads, 0.5), (Tails, 0.5)]
+coin = Prob [(Heads, 0.5), (Tails, 0.5)]
 unfair_coin :: Prob Coin
-unfair_coin = [(Heads, 0.6), (Tails, 0.4)]
+unfair_coin = Prob [(Heads, 0.6), (Tails, 0.4)]
 flip :: Prob [Coin]
@@ Line 271: / Line 271: @@
 die n = undefined
--- (die 20) <*> (die 6) -- the probability distribution of rolling a d20 followed by a d6
+-- (,) <$> (die 20) <*> (die 6) -- the probability distribution of rolling a d20 followed by a d6
 </code>
 **11.4.5.** Let's use this framework to solve a M3 problem: "Jo has took a test for a disease. The result of the test is either positive or negative and the test is 95% reliable: in 95% of cases of people who really have the disease, a positive result is returned, and in 95% of cases of people who do not have the disease, a negative result is obtained. 1% of people of Jo’s age and background have the disease. Jo took the test, and the result is positive. What is the probability that Jo has the disease?"