[Conflict resolve nordland@csee.ltu.se**20081111141619] { hunk ./examples/MasterMind_descr.html 1 - - - - - -

MasterMind

-MasterMind is a board game with two players; in this -case the user choses the secret and the program does the guessing. -Here is a sample interaction: -
-examples> ./MasterMind
-Welcome to Mastermind!
-Choose your secret. Press return when ready.
-
-My guess: Red Blue Blue Red
-Answer (two integers): 1 1
-My guess: Blue Black Yellow Red
-Answer (two integers): 2 0
-My guess: Green Black Red Red
-Answer (two integers): 0 0
-My guess: Blue Blue Yellow White
-Answer (two integers): 3 0
-My guess: Blue Blue Yellow Blue
-Answer (two integers): 3 0
-My guess: Blue Blue Yellow Yellow
-Answer (two integers): 4 0
-Yippee!
-Do you want to play again? (y/n) n
-examples> 
-
-The program is too long to display here. We only note a few things: - - - rmfile ./examples/MasterMind_descr.html hunk ./examples/Primes_descr.html 1 - - - -Primes - - - -

Primes

-

-As a reactive program, this is quite degenerate: when started, it -expects -a positive integer n>2 as command line argument. It -computes all primes smaller than or equal to n, prints -the number of such primes to stdout and terminates. -

-The algorithm used illustrates imperative programming using updatable -arrays in Timber. Here is the program: -

-
-module Primes where
-
-import POSIX 
-
-root env = class
-   limit :: Int
-   limit = parse (env.argv!1)
-   primesBound = limit `div` log3 limit
-
-   primes := uniarray primesBound 0
-   count  := 0
-
-   isPrime k = loop 0
-      where loop n = do 
-              p = primes!n
-              if p*p > k then
-                 result True
-              elsif k `mod` p  == 0 then
-                 result False
-              else loop (n+1)
-
-   checkFrom k = do
-     p <- isPrime k
-     if p then 
-        primes!count := k
-        count := count + 1
-     if k < limit then checkFrom (k+1)
-
-   result action
-     primes!0 := 2
-     count := 1
-     checkFrom 3
-     env.stdout.write (show count++"\n")
-     env.exit 0
-
-
-log3 :: Int -> Int
-log3 n  
-  | n < 3       = 0
-  | otherwise   = 1 + log3 (n `div` 3)
-
-
-
-Prime numbers are stored in array primes, which is -initialised with all zeros (primitive function uniarray -creates an array, whose size is given by the first argument, where -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 n is at most n `div` log3 n. -

-The root action notes that 2 is a prime and initiates count -to 1; it then checks numbers for primeness, starting with 3 in -procedure checkFrom. The iterative check is expressed using -recursion, checking for successive numbers up to limit. -

-The procedure isPrime works by trial division, using already -discovered primes: to check whether k is a prime, one tries -to find a proper prime factor p such that p*p <= k. If -none is found, k is prime. - - - rmfile ./examples/Primes_descr.html hunk ./examples/menu.html 1 - - - - - - - -

-

Timber examples

- -
- - -