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Running other programs in the Haskell / Linear package

I have a program called LPSolvethat solves the problems of mixed one-piece optimization. The problem is that I cannot dynamically add constraints during iterations, so I would like to write a Haskell program that uses LPSolveto solve relaxation, and then derive additional constraints based on the solutions. Constraints that use the problem structure.

Is it possible to run the executable in Haskell and get the output sent to the terminal?

Is there a Haskell package that solves linear programming problems?

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3 answers

runInteractiveProcess "" stdin/stdout

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Shelly . Haskell, , . , .

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You can use GLPK and create and run problems in Haskell code

-- Usando GLPK, http://www.gnu.org/software/glpk/ 
import Data.List 
import Data.Maybe 
import Control.Monad 
import Data.LinearProgram 
import Data.LinearProgram.GLPK 
import qualified Data.Map as M 

-- Sólo por dar nombre a las varibles 
x e = "X" ++ show e 

-- Resuelve el problema de elegir el menor número de empleados 
solveEmployees :: [(Int, Int)] -> LP String Int 
solveEmployees es = execLPM $ do  setDirection Min 
                                  setObjective $ linCombination $ map (\e -> (1, x e)) emps 
                                  mapM_ (\(a, b) -> geqTo (varSum [x a, x b]) 1) es 
                                  mapM_ (\n -> setVarKind (x n) BinVar) emps 
                                  where emps = nub $ map fst es ++ map snd es 

-- Wrapper suponiendo que siempre hay solución (aquí siempre) 
getEmployees :: [(Int, Int)] -> IO [Int] 
getEmployees es = do 
  (_, Just (_, m)) <- glpSolveVars mipDefaults $ solveEmployees es 
  return $ map (read.tail.fst). M.toList. M.filter (==1) $ m 

-- Tráfico de influencias, intentaremos que el empleado 'e' vaya a la playa 
--       (da igual que sea de Estocolmo o de Londres) 
getEmployees' :: Int -> [(Int, Int)] -> IO [Int] 
getEmployees' e es = do 
  r <- getEmployees es 
  r' <- getEmployees $ filter (\(a, b ) -> a /= e && b /= e) es 
  return $ if length r == 1 + length r' then e: r' else r 

-- Test 
main = do 
  putStrLn $ "Input: " ++ show test2 
  putStrLn "Testing: solveEmployees" 
  r1 <- getEmployees test2 
  putStrLn $ show r1 
  putStrLn "Testing: solveEmployees' 2001" 
  r2 <- getEmployees' 2001 test2 
  putStrLn $ show r2 

test1 :: [(Int, Int)] 
test1 = [(1009, 2011), (1017, 2011)] 

test2 :: [(Int, Int)] 
test2 = [(1009, 2000), (1009, 2001), (1008, 2000), (1008, 2001)]
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