Merge pull request #10 from turion/more_koans

More koans

TODO.md

@@ -7,6 +7,7 @@
 ## CI
 
 * Check cabal outdated
+* Check in diffs between solution and problem and make sure it is stable (such that every fix in a solution gets propagated to the problem and vice versa)
 
 # Content
 ## Basic
@@ -46,6 +47,9 @@
 * Complicated clock errors
     * Order of components (including a RB) is not the same as order of clocks in Rhine, this gives a weird error that `HasClock cl '[]` cannot be satisfied
 * Write your own backend to some library
+* Complicated Arrow syntax
+    * scoping of live and static values
+    * Nested if then else & do blocks
 
 ## Data analysis track
 

koans/basic/2/3-count-the-lines/Koan.hs

@@ -14,7 +14,7 @@ The 'count' signal function has internal state, the current count.
 Every time it is called (because 'StdinClock' has ticked),
 the count is incremented and returned.
 -}
-lineCount :: ClSF IO StdinClock () Integer
+lineCount :: ClSF IO StdinClock () Int
 lineCount = count -- This is part of the library!
 
 -- | Print the number of the line that was just entered.

koans/basic/2/3-count-the-lines/solution/Koan.hs

@@ -14,7 +14,7 @@ The 'count' signal function has internal state, the current count.
 Every time it is called (because 'StdinClock' has ticked),
 the count is incremented and returned.
 -}
-lineCount :: ClSF IO StdinClock () Integer
+lineCount :: ClSF IO StdinClock () Int
 lineCount = count -- This is part of the library!
 
 -- | Print the number of the line that was just entered.

koans/basic/2/5-count-all-the-chars/Koan.hs

@@ -33,9 +33,14 @@ userInput = tagS
 wordCount :: ClSF IO StdinClock () Int
 wordCount = userInput >-> arr (Text.words >>> length)
 
--- | Output the number of characters of the line that was just entered.
+{- | Output the number of characters of the line that was just entered.
+
+The newline character is not part of 'userInput',
+therefore +1 is added for it.
+-}
 charCount :: ClSF IO StdinClock () Int
-charCount = userInput >-> arr Text.length
+-- Yes, you can use >>> to compose ordinary functions as well!
+charCount = userInput >-> arr (Text.length >>> (+ 1))
 
 -- | Compute the sum of all input numbers so far, including the current one.
 sumClSF :: (Monad m, Num a) => ClSF m cl a a

koans/basic/2/5-count-all-the-chars/solution/Koan.hs

@@ -33,9 +33,14 @@ userInput = tagS
 wordCount :: ClSF IO StdinClock () Int
 wordCount = userInput >-> arr (Text.words >>> length)
 
--- | Output the number of characters of the line that was just entered.
+{- | Output the number of characters of the line that was just entered.
+
+The newline character is not part of 'userInput',
+therefore +1 is added for it.
+-}
 charCount :: ClSF IO StdinClock () Int
-charCount = userInput >-> arr Text.length
+-- Yes, you can use >>> to compose ordinary functions as well!
+charCount = userInput >-> arr (Text.length >>> (+ 1))
 
 -- | Compute the sum of all input numbers so far, including the current one.
 sumClSF :: (Monad m, Num a) => ClSF m cl a a

koans/basic/2/5-count-all-the-chars/test/Test.hs

@@ -20,9 +20,9 @@ main :: IO ()
 main = testForSecondsInput 1 testLines Koan.main $ \output ->
   case output of
     [] -> ["Weird, your program didn't produce any output!"]
-    _ | output == (tshow @Int <$> [2, 11, 5, 20, 6, 24]) -> []
+    _ | output == (tshow @Int <$> [2, 12, 5, 22, 6, 27]) -> []
     _
-      | output == (tshow @Int <$> [11, 2, 20, 5, 24, 6]) ->
+      | output == (tshow @Int <$> [12, 2, 22, 5, 27, 6]) ->
           ["Nearly there, it seems you've swapped characters and words around."]
     _ ->
       [ "The program produced output, but it wasn't quite right."

koans/basic/2/6-count-everything/Koan.hs

@@ -0,0 +1,70 @@
+{- | Count everything!
+
+If we can count words, characters, and lines, let's just put it all together.
+This is a bit finicky, but give it a try nevertheless!
+Remember the combinator for parallel composition:
+
+@
+(&&&) :: Monad m => ClSF m cl a b -> ClSF m cl a c -> ClSF m cl a (b, c)
+@
+-}
+module Koan where
+
+-- text
+import Data.Text (Text)
+import Data.Text qualified as Text (length, words)
+
+-- rhine
+import FRP.Rhine hiding (currentInput)
+
+-- | A line of user input.
+userInput :: ClSF IO StdinClock () Text
+userInput = tagS
+
+-- | Output the number of words of the line that was just entered.
+wordCount :: ClSF IO StdinClock () Int
+wordCount = userInput >-> arr (Text.words >>> length)
+
+{- | Output the number of characters of the line that was just entered.
+
+The newline character is not part of 'userInput',
+therefore +1 is added for it.
+-}
+charCount :: ClSF IO StdinClock () Int
+-- Yes, you can use >>> to compose ordinary functions as well!
+charCount = userInput >-> arr (Text.length >>> (+ 1))
+
+-- | Compute the sum of all input numbers so far, including the current one.
+sumClSF :: (Monad m, Num a) => ClSF m cl a a
+sumClSF = feedback 0 $ arr aggregator
+  where
+    aggregator :: (Num a) => (a, a) -> (a, a)
+    aggregator (currentInput, currentSum) =
+      let
+        nextSum = currentInput + currentSum
+       in
+        (nextSum, nextSum)
+
+-- | The number of lines of input so far.
+lineCount :: ClSF IO StdinClock () Integer
+lineCount = count
+
+-- | The number of words of input so far.
+totalWordCount :: ClSF IO StdinClock () Int
+totalWordCount = wordCount >-> sumClSF
+
+-- | The number of characters of input so far.
+totalCharCount :: ClSF IO StdinClock () Int
+totalCharCount = charCount >-> sumClSF
+
+-- | The number of total lines, words and characters so far.
+totalCount :: ClSF IO StdinClock () _ -- What will the type of this be?
+totalCount = _ &&& _ &&& _
+
+-- | Print the number of total words and characters so far.
+printAllCounts :: ClSF IO StdinClock () ()
+-- On what do you need to pattern match here to bring lines_, words_ and chars into scope?
+printAllCounts = totalCount >-> arrMCl (\_ -> print lines_ >> print words_ >> print chars)
+
+main :: IO ()
+main = flow $ printAllCounts @@ StdinClock

koans/basic/2/6-count-everything/solution/Koan.hs

@@ -0,0 +1,70 @@
+{- | Count everything!
+
+If we can count words, characters, and lines, let's just put it all together.
+This is a bit finicky, but give it a try nevertheless!
+Remember the combinator for parallel composition:
+
+@
+(&&&) :: Monad m => ClSF m cl a b -> ClSF m cl a c -> ClSF m cl a (b, c)
+@
+-}
+module Koan where
+
+-- text
+import Data.Text (Text)
+import Data.Text qualified as Text (length, words)
+
+-- rhine
+import FRP.Rhine hiding (currentInput)
+
+-- | A line of user input.
+userInput :: ClSF IO StdinClock () Text
+userInput = tagS
+
+-- | Output the number of words of the line that was just entered.
+wordCount :: ClSF IO StdinClock () Int
+wordCount = userInput >-> arr (Text.words >>> length)
+
+{- | Output the number of characters of the line that was just entered.
+
+The newline character is not part of 'userInput',
+therefore +1 is added for it.
+-}
+charCount :: ClSF IO StdinClock () Int
+-- Yes, you can use >>> to compose ordinary functions as well!
+charCount = userInput >-> arr (Text.length >>> (+ 1))
+
+-- | Compute the sum of all input numbers so far, including the current one.
+sumClSF :: (Monad m, Num a) => ClSF m cl a a
+sumClSF = feedback 0 $ arr aggregator
+  where
+    aggregator :: (Num a) => (a, a) -> (a, a)
+    aggregator (currentInput, currentSum) =
+      let
+        nextSum = currentInput + currentSum
+       in
+        (nextSum, nextSum)
+
+-- | The number of lines of input so far.
+lineCount :: ClSF IO StdinClock () Integer
+lineCount = count
+
+-- | The number of words of input so far.
+totalWordCount :: ClSF IO StdinClock () Int
+totalWordCount = wordCount >-> sumClSF
+
+-- | The number of characters of input so far.
+totalCharCount :: ClSF IO StdinClock () Int
+totalCharCount = charCount >-> sumClSF
+
+-- | The number of total lines, words and characters so far.
+totalCount :: ClSF IO StdinClock () (Integer, (Int, Int)) -- What will the type of this be?
+totalCount = lineCount &&& totalWordCount &&& totalCharCount
+
+-- | Print the number of total words and characters so far.
+printAllCounts :: ClSF IO StdinClock () ()
+-- On what do you need to pattern match here to bring lines_, words_ and chars into scope?
+printAllCounts = totalCount >-> arrMCl (\(lines_, (words_, chars)) -> print lines_ >> print words_ >> print chars)
+
+main :: IO ()
+main = flow $ printAllCounts @@ StdinClock

koans/basic/2/6-count-everything/test/Test.hs

@@ -0,0 +1,30 @@
+module Main where
+
+-- text
+import Data.Text as Text
+
+-- koan
+import Koan qualified (main)
+
+-- test-io
+import TestIO
+
+testLines :: [Text]
+testLines =
+  [ "Hello Rhine"
+  , "this is a"
+  , "test"
+  ]
+
+main :: IO ()
+main = testForSecondsInput 1 testLines Koan.main $ \output ->
+  case output of
+    [] -> ["Weird, your program didn't produce any output!"]
+    _ | output == (tshow @Int <$> [1, 2, 12, 2, 5, 22, 3, 6, 27]) -> []
+    _ ->
+      [ "The program produced output, but it wasn't quite right."
+      , "It received the following input:"
+      ]
+        ++ testLines
+        ++ ["And it returned:"]
+        ++ output

koans/basic/2/7-count-everything-nicer/Koan.hs

@@ -0,0 +1,81 @@
+{-# LANGUAGE CPP #-}
+
+-- Disabling formatter and linter because it would fail on the syntax error otherwise.
+#ifndef __HLINT__
+{- FOURMOLU_DISABLE -}
+
+-- Start reading here
+-- vvvvvvvvvvvvvvvvvv
+
+{- | Count everything nicer.
+
+The last problem got quite verbose, and fiddling around with nested tuples isn't fun.
+Fortunately, Haskell has a language extension that provides very useful syntax
+for data flow constructs like signal functions!
+It is called "arrow notation", and you can read a bit more about it here: https://www.haskell.org/arrows/.
+Have a look how the code of the previous koan can be cleaned up with it.
+-}
+module Koan where
+
+-- text
+import Data.Text qualified as Text (length, words)
+
+-- rhine
+import FRP.Rhine hiding (currentInput)
+
+-- | Compute the sum of all input numbers so far, including the current one.
+sumClSF :: (Monad m, Num a) => ClSF m cl a a
+sumClSF = feedback 0 $ arr aggregator
+  where
+    aggregator :: (Num a) => (a, a) -> (a, a)
+    aggregator (currentInput, currentSum) =
+      let
+        nextSum = currentInput + currentSum
+       in
+        (nextSum, nextSum)
+
+-- | Print the number of total words and characters so far.
+printAllCounts :: ClSF IO StdinClock () ()
+-- proc is a keyword. Think of it like a lambda expression!
+-- But why does GHC spit out a nasty parse error here?
+-- Read through the following to find out!
+printAllCounts = proc () -> do
+  -- This is nearly like do notation, except it also has syntax for input, the -<.
+
+  -- /------/--- Everything left from a <- is the output _signal_ of a signal function.
+  -- |      |    It is a value that can depend on the current tick of the clock.
+  -- |      |
+  -- |      |   /--- Signal functions can be used between <- and -<.
+  -- |      |   |
+  -- |      |   |       /--- This is the input to the signal function. (tagS needs none.)
+  -- |      |   |       |
+  -- v      v   v       v
+  userInput <- tagS -< ()
+
+  -- We can apply ordinary functions to signals.
+  let wordCount = length $ Text.words userInput
+      charCount = Text.length userInput + 1
+
+  lineCount <- count @Int -< ()
+
+  -- Signals can be inputs to signal functions.
+  -- This way we can aggregate signals.
+  totalWordCount <- sumClSF -< wordCount
+  totalCharCount <- sumClSF -< charCount
+
+  -- If a signal function has trivial output (), the <- is not needed.
+  arrMCl print -< lineCount
+  arrMCl print -< totalWordCount
+  arrMCl print -< _ -- Which one is missing here?
+
+-- As you've seen, arrow notation introduces two new syntactic constructions,
+-- the proc keyword an the -< operator.
+-- You need to turn on a GHC language extension so that they can be parsed!
+-- Can you uncomment the following line, and move to the top of the file?
+-- {-# LANGUAGE Arrows #-}
+
+main :: IO ()
+main = flow $ printAllCounts @@ StdinClock
+
+-- Ignore the next line ;)
+#endif