[additions to directory examples
sydow@chalmers.se**20081111100156] {
move ./examples/RandomGenerator.t ./lib/RandomGenerator.t
hunk ./examples/HashTable.t 1
-module HashTable where
-
-struct Dictionary a b where
-  insert :: a -> b -> Action
-  lookup :: a -> Request (Maybe b)
-
-{-
-
-Wrong design; String should not have ONE hash function.
-Better to give hash function as arg to hashDict.
-
-class Hashable a =
-  hash :: a -> Int -> Int
-  -- requirement: 0 <= hash a n < n
-
--}
-
-sequ []       = class result []
-sequ (x:xs)   = class
-                   y = new x
-                   ys = new sequ xs
-                   result (y:ys)
-
-hashDict hash dictT n = class
-  ds = new sequ (replicate n dictT)
-
-  dict = array ds
-  
-  insert a b = action
-    (dict!(hash a n)).insert a b
-
-  lookup a = request
-    (dict!(hash a n)).lookup a
-   
-  result Dictionary {..}
-
-{-
-hashDict1 hash dictT n = do
-  ds <- sequence (replicate n dictT)  
-
-  dict = array ds
-  
-  insert a b = (dict!(hash a n)).insert a b
-
-  lookup a = (dict!(hash a n)).lookup a
-   
-  result Dictionary {..}
--}
rmfile ./examples/HashTable.t
hunk ./examples/MasterMind_descr.html 7
-<a href="">MasterMind</a> is a board game with two players; in this
-case the user choses the secret and the program does the guessing.
+<a href="http://en.wikipedia.org/wiki/Mastermind_(board_game)">MasterMind</a> is a board game with two players; in this
+case the user choses the secret and the program does the
+guessing. Unfortunately, the board is not visualised. 
hunk ./examples/Primes.t 22
-   tryFrom k = do
+   checkFrom k = do
hunk ./examples/Primes.t 25
-        count := count + 1
hunk ./examples/Primes.t 26
-     if k < limit then tryFrom (k+1)
+        count := count + 1
+     if k < limit then checkFrom (k+1)
hunk ./examples/Primes.t 31
-     tryFrom 3
-     env.stdout.write (show (count+1)++"\n")
+     count := 1
+     checkFrom 3
+     env.stdout.write (show count++"\n")
hunk ./examples/Primes_descr.html 63
+<ul>
+  <li>
hunk ./examples/Primes_descr.html 68
-all elements are initialised to the value of the second argument
-The program uses the moderately clever bound that the number
-of primes up to <tt>n</tt> is at most <tt>n `div` log3 n</tt>.
-<p>
+all elements are initialised to the value of the second argument).
+<li>
hunk ./examples/Primes_descr.html 72
-procedure <tt>checkFrom</tt>. The iterative check is expressed using
-recursion, checking for successive numbers up to <tt>limit</tt>.
-<p>
+procedure <tt>checkFrom</tt>. 
+<li>
hunk ./examples/Primes_descr.html 77
-none is found, <tt>k</tt> is prime. 
-
+none is found, <tt>k</tt> is prime.
+<li>
+The iterative check of all integers in range for primeness is expressed using
+recursion in <tt>checkFrom</tt>. Alternatively, we could omit procedure
+<tt>checkFrom</tt>,
+in favour of an iterative construction in the resulting action:
+<pre>
+   result action
+     primes!0 := 2
+     count := 1
+     forall k <- [3..limit] do
+       p <- isPrime k
+       if p then 
+         count := count + 1
+         primes!count := k
+     env.stdout.write (show (count+1)++"\n")
+     env.exit 0
+</pre>
+The choice has negligible effect on efficiency (the tail recursive
+<tt>checkFrom</tt> is transformed to iteration by the compiler),
+but is merely a matter of taste.
+</ul>
+<p> We end by noting two mathematical facts that the program relies
+on:
+<ul>
+  <li> To limit the size of the array of primes,
+the program uses the moderately clever bound that the number
+of primes up to <tt>n</tt> is less than <tt>n `div` log3 n</tt>.
+  <li>Correctness of the algorithm <tt>isPrime</tt> depends on the fact that
+if <tt>k</tt> is actually a prime, then there is a smaller prime
+<tt>p</tt> with <tt>p*p > k</tt>. In fact, by Bertrand's postulate,
+much more is true: there is a prime <tt>p > k `div` 2</tt>.
+  </ul>
hunk ./examples/TCPClient.t 13
-        env.stdout.write "Connecting..."
+        env.stdout.write "Connecting... "
hunk ./examples/TCPClient.t 27
-          env.stdout.write "Server closing; Bye!\n"
-          env.exit 0
+         env.stdout.write ("Server closing after "++show rounds++" rounds\n")
+         env.exit 0
hunk ./examples/TCPClient.t 31
-          case str of 
-            [] -> sock.inFile.close
-                  env.stdout.write ("Server closing after "++show rounds++" rounds\n")
-                  env.exit 0
-                  rounds := rounds+1
-            _  -> env.stdout.write (str ++ "\n")
+         env.stdout.write (str ++ "\n")
+         rounds := rounds + 1
hunk ./examples/TCPClient.t 35
-          sock.outFile.write (init str)
+         sock.outFile.write (init str)
hunk ./examples/TCPClient.t 38
-            env.stdout.write "Hello!\n"
-            env.stdin.installR echo
-            sock.inFile.installR receive
+          env.stdout.write "Hello!\n"
+          env.stdin.installR echo
+          sock.inFile.installR receive
hunk ./examples/TCPClient.t 44
-
-  init [x] = []
-  init (x :xs) = x : init xs
-
hunk ./examples/intro.html 22
+<p>
hunk ./examples/intro.html 44
-  <li> <tt>EchoServer</tt>. A variation of the previous: limiting
+  <li> <tt>EchoServer2</tt>. A variation of the previous: limiting
hunk ./examples/intro.html 49
+  <li> <tt>Primes</tt>. As a reactive program, a quite degenerate example:
+  the program computes the primes up to a given bound and terminates.
hunk ./examples/menu.html 20
+<li><a href="Primes_descr.html" target = "main">Primes</a></li>
}