Сопоставление языков программирования Часть 7. Haskell

$ yum list ghc 
Доступные пакеты 
ghc.i686   7.6.3-18.3.fc20     updates 
$ sudo yum install ghc 
...
Установить  1 пакет (+47 зависимых) 
Объем загрузки: 82 M 
Объем изменений: 610 M 
...
Установлено: 
  ghc.i686 0:7.6.3-18.3.fc20 
$ ghc --version 
The Glorious Glasgow Haskell Compilation System, version 7.6.3

# ghci 
GHCi, version 7.6.3: http://www.haskell.org/ghc/  :? for help 
Loading package ghc-prim ... linking ... done. 
Loading package integer-gmp ... linking ... done. 
Loading package base ... linking ... done. 
Prelude> 2+2 
4 
Prelude> ^D 
Leaving GHCi.

$ yum list cabal* 
Загружены модули: langpacks, refresh-packagekit 
Доступные пакеты 
cabal-dev.i686      0.9.2-2.fc20                       fedora 
cabal-install.i686    1.16.0.2-27.fc20              updates 
cabal-rpm.i686          0.8.7-1.fc20                   updates 
$ sudo yum install cabal* 
...
Установить  3 пакета (+13 зависимых) 
Объем загрузки: 1.7 M 
Объем изменений: 9.1 M 
...
Выполнено!

$ cabal --help 
...
Commands: 
  install      Installs a list of packages. 
  update       Updates list of known packages 
  list         List packages matching a search string. 
  info         Display detailed information about a particular package. 
  fetch        Downloads packages for later installation. 
  unpack       Unpacks packages for user inspection. 
  check        Check the package for common mistakes 
  sdist        Generate a source distribution file (.tar.gz). 
  upload       Uploads source packages to Hackage 
  report       Upload build reports to a remote server. 
  init         Interactively create a .cabal file. 
  configure    Prepare to build the package. 
  build        Make this package ready for installation. 
  copy         Copy the files into the install locations. 
  haddock      Generate Haddock HTML documentation. 
  clean        Clean up after a build. 
  hscolour     Generate HsColour colourised code, in HTML format. 
  register     Register this package with the compiler. 
  test         Run the test suite, if any (configure with UserHooks). 
  bench        Run the benchmark, if any (configure with UserHooks). 
  upgrade      (command disabled, use install instead) 
  help         Help about commands 
...
$ cabal update 
Downloading the latest package list from hackage.haskell.org 
Note: there is a new version of cabal-install available. 
To upgrade, run: cabal install cabal-install

$ cabal list complex 
* complex-generic 
    Synopsis: complex numbers with non-mandatory RealFloat 
    Default available version: 0.1.1 
    Installed versions: [ Not installed ] 
    Homepage: https://gitorious.org/complex-generic 
    License:  BSD3 

* complex-integrate 
    Synopsis: A simple integration function to integrate a complex-valued 
              complex functions 
    Default available version: 1.0.0 
    Installed versions: [ Not installed ] 
    Homepage: https://github.com/hijarian/complex-integrate 
    License:  PublicDomain 

* complexity 
    Synopsis: Empirical algorithmic complexity 
    Default available version: 0.1.3 
    Installed versions: [ Not installed ] 
    License:  BSD3 

* storable-complex 
    Synopsis: Storable instance for Complex 
    Default available version: 0.2.1 
    Installed versions: [ Not installed ] 
    License:  BSD3

$ cabal list >> cabal.lst 
$ ls -l cabal.lst 
-rw-rw-r--. 1 Olej Olej 1273606 мар  9 11:40 cabal.lst 
$ wc -l cabal.lst 
41520 cabal.lst

$ mkdir triangle 
$ cd triangle 
$ mkdir src 
$ cd src
$ touch Main.hs 
$ cd ..
$ tree 
. 
└── src 
    └── Main.hs

$ cabal init 
Package name? [default: triangle] 
Package version? [default: 0.1.0.0] 
Please choose a license: 
 * 1) (none) 
   2) GPL-2 
   3) GPL-3 
   4) LGPL-2.1 
   5) LGPL-3 
   6) BSD3 
   7) MIT 
   8) Apache-2.0 
   9) PublicDomain 
  10) AllRightsReserved 
  11) Other (specify) 
Your choice? [default: (none)] 7 
Author name? 
Maintainer email? 
Project homepage URL? 
Project synopsis? 
Project category: 
 * 1) (none) 
   2) Codec 
   3) Concurrency 
   4) Control 
   5) Data 
   6) Database 
   7) Development 
   8) Distribution 
   9) Game 
  10) Graphics 
  11) Language 
  12) Math 
  13) Network 
  14) Sound 
  15) System 
  15) System 
  16) Testing 
  17) Text 
  18) Web 
  19) Other (specify) 
Your choice? [default: (none)] 
What does the package build: 
   1) Library 
   2) Executable 
Your choice? 2 
Include documentation on what each field means (y/n)? [default: n] 

Guessing dependencies... 

Generating LICENSE... 
Warning: unknown license type, you must put a copy in LICENSE yourself. 
Generating Setup.hs... 
Generating triangle.cabal... 

Warning: no synopsis given. You should edit the .cabal file and add one. 
You may want to edit the .cabal file and add a Description field. 
$ tree 
. 
├── Setup.hs 
├── src 
│   └── Main.hs 
└── triangle.cabal

...
executable triangle 
  ghc-options:         -W 
  main-is:             Main.hs 
  build-depends:       haskell98 >=2.0.0.2 , exceptions 
...

$ cabal configure 
Resolving dependencies... 
Configuring triangle-0.1.0.0... 
Warning: The 'license-file' field refers to the file 'LICENSE' which does not exist.

module Main where 
import Complex 
import Numeric 
import IO 

{- код проверен для версии: 
$ ghc --version 
The Glorious Glasgow Haskell Compilation System, version 7.6.3 
-} 

type Point = Complex Double       -- синоним координатной точки 

get_coord :: String -> Point      -- декодирование строки ввода в координаты x % y 
get_coord str = 
   f( words str ) 
   where 
      f :: [String] -> Point 
      f lst = ( ( read( lst !! 0 ) :: Double ) :+ ( read( lst !! 1 ) :: Double ) ) 

try_to_input :: IO String         -- ввод строки с ожиданием ^D 
try_to_input = do 
   line <- hGetLine stdin `catch` (\e -> if IO.isEOFError e then return 
   [] else ioError e) 
   return line 

get_shape :: [Point] -> IO [Point] 
get_shape shape = do              -- рекурсивный ввод списка вершин 
   let pos = length( shape ) + 1 
   putStr( "вершина № " ++ show( pos ) ++ " : " ) 
   hFlush stdout 
   line <- try_to_input 
   if length( line ) == 0 then return shape else get_shape( get_coord( line ) : shape ) 

showP = \p -> "[" ++ ( showFFloat ( Just 2 ) ( realPart( p ) ) "" ) ++ 
              "," ++ ( showFFloat ( Just 2 ) ( imagPart( p ) ) "" ) ++ "] " 

show_shape :: [Point] -> String 
show_shape (x:xs) = 
   if length xs == 0 then showP x else ( showP x ) ++ show_shape( xs ) 

perimeter :: [Point] -> Double 
perimeter shape = 
   summa shape 0.0 
   where distance = \ p1 p2 -> magnitude( p1 - p2 ) 
         summa :: [Point] -> Double -> Double 
         summa (y:ys) perim       -- локальная функция накопления длин сторон 
            | length( ys ) == 0 = ( distance y $ head shape ) + perim 
            | otherwise = ( distance y $ head ys ) + summa ys perim 

square :: [Point] -> Double 
square (y:ys) = 
   summa y ys 0.0 
   where summa :: Point -> [Point] -> Double -> Double 
         summa top shape squa     -- локальная функция накопления площади 
            | length( tail shape ) == 0 = squa 
            | otherwise = ( triang top shape ) + summa top ( tail shape ) squa 
         triang :: Point -> [Point] -> Double 
         triang top (z:zs) =      -- локальная функция площадь треугольника 
            ( magnitude side1 ) * ( magnitude side2 ) * 
            ( abs $ sin( phase side1 - phase side2 ) ) * 0.5 
            where side1 = z - top 
                  side2 = z - head zs 

next_shape :: IO ()               -- цикл рассчёта 
next_shape = do 
   putStrLn( "координаты вершин в формате: X Y" ) 
   shape <- get_shape [] 
   putStrLn $ "\rвершин " ++ show( length shape ) ++ " : " ++ show_shape shape 
   putStrLn( "периметр = " ++ showFFloat ( Just 2 ) ( perimeter shape ) "" ) 
   putStrLn( "площадь = " ++ showFFloat ( Just 2 ) ( square shape ) "" ) 
   putStrLn $ "---------------------------------" 
   next_shape 

main :: IO () 
main = do next_shape              -- запуск цикла программы

$ cabal build 
Building triangle-0.1.0.0... 
Preprocessing executable 'triangle' for triangle-0.1.0.0... 
[1 of 1] Compiling Main ( src/Main.hs, dist/build/triangle/triangle-tmp/Main.o ) 
src/Main.hs:3:1: Warning: 
    The import of `Numeric' is redundant 
      except perhaps to import instances from `Numeric' 
    To import instances alone, use: import Numeric() 
src/Main.hs:42:1: Warning: 
    Pattern match(es) are non-exhaustive 
    In an equation for `show_shape': Patterns not matched: [] 
src/Main.hs:50:10: Warning: 
    Pattern match(es) are non-exhaustive 
    In an equation for `summa': Patterns not matched: [] _ 
src/Main.hs:55:1: Warning: 
    Pattern match(es) are non-exhaustive 
    In an equation for `square': Patterns not matched: [] 
src/Main.hs:62:10: Warning: 
    Pattern match(es) are non-exhaustive 
    In an equation for `triang': Patterns not matched: _ [] 
Linking dist/build/triangle/triangle ...

$ tree 
. 
├── dist 
│   ├── build 
│   │   ├── autogen 
│   │   │   ├── cabal_macros.h 
│   │   │   └── Paths_triangle.hs 
│   │   └── triangle 
│   │       ├── triangle 
│   │       └── triangle-tmp 
│   │           ├── Main.hi 
│   │           └── Main.o 
│   ├── package.conf.inplace 
│   └── setup-config 
├── Setup.hs 
├── src 
│   └── Main.hs 
└── triangle.cabal

$ ./dist/build/triangle/triangle 
координаты вершин в формате: X Y 
вершина № 1 : 1.00001 1.00003 
вершина № 2 : 1.00003 2.0003 
вершина № 3 : 2.0004 1.00005 
вершин 3 : [2.00,1.00] [1.00,2.00] [1.00,1.00] 
периметр = 3.42 
площадь = 0.50 
--------------------------------- 
координаты вершин в формате: X Y 
вершина № 1 : ^C

$ cabal clean 
cleaning...

module Main where 
import System.Environment 

main :: IO () 
main = do             -- сама программа 
     args <- getArgs  {- вложенный комментарий -} 
     putStrLn( "Привет от Haskell, " ++ args !! 0 )

$ ghc -o hello_hs hello_hs.hs 
[1 of 1] Compiling Main             ( hello_hs.hs, hello_hs.o ) 
Linking hello_hs ...