Εργαστήριο 3 στη Ηaskell

Εξάσκηση (εκφωνήσεις και λύσεις ασκήσεων)

Άσκηση H3E1 Διαβάστε το Inside the Cult of the Haskell Programmer από το περιοδικό WIRED. Συμπληρώστε τον κώδικα που φαίνεται στο σχήμα του άρθρου σε ένα πρόγραμμα σε Haskell έτσι ώστε να εμφανίζει στην οθόνη αυτό που πιστεύετε ότι είναι ο σκοπός του.

Λύση άσκησης Η3Ε1

primes :: [Integer]
primes = sieve [2..]
    where 
        sieve (p:xs) = p: sieve [n | n <- xs, n `mod` p /= 0 ] 

main :: IO ()
main = do
    print(take 1000 primes)

Μεταγλώττιση και εκτέλεση:

$ runghc h3e1.hs
[2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009,1013,1019,1021,1031,1033,1039,1049,1051,1061,1063,1069,1087,1091,1093,1097,1103,1109,1117,1123,1129,1151,1153,1163,1171,1181,1187,1193,1201,1213,1217,1223,1229,1231,1237,1249,1259,1277,1279,1283,1289,1291,1297,1301,1303,1307,1319,1321,1327,1361,1367,1373,1381,1399,1409,1423,1427,1429,1433,1439,1447,1451,1453,1459,1471,1481,1483,1487,1489,1493,1499,1511,1523,1531,1543,1549,1553,1559,1567,1571,1579,1583,1597,1601,1607,1609,1613,1619,1621,1627,1637,1657,1663,1667,1669,1693,1697,1699,1709,1721,1723,1733,1741,1747,1753,1759,1777,1783,1787,1789,1801,1811,1823,1831,1847,1861,1867,1871,1873,1877,1879,1889,1901,1907,1913,1931,1933,1949,1951,1973,1979,1987,1993,1997,1999,2003,2011,2017,2027,2029,2039,2053,2063,2069,2081,2083,2087,2089,2099,2111,2113,2129,2131,2137,2141,2143,2153,2161,2179,2203,2207,2213,2221,2237,2239,2243,2251,2267,2269,2273,2281,2287,2293,2297,2309,2311,2333,2339,2341,2347,2351,2357,2371,2377,2381,2383,2389,2393,2399,2411,2417,2423,2437,2441,2447,2459,2467,2473,2477,2503,2521,2531,2539,2543,2549,2551,2557,2579,2591,2593,2609,2617,2621,2633,2647,2657,2659,2663,2671,2677,2683,2687,2689,2693,2699,2707,2711,2713,2719,2729,2731,2741,2749,2753,2767,2777,2789,2791,2797,2801,2803,2819,2833,2837,2843,2851,2857,2861,2879,2887,2897,2903,2909,2917,2927,2939,2953,2957,2963,2969,2971,2999,3001,3011,3019,3023,3037,3041,3049,3061,3067,3079,3083,3089,3109,3119,3121,3137,3163,3167,3169,3181,3187,3191,3203,3209,3217,3221,3229,3251,3253,3257,3259,3271,3299,3301,3307,3313,3319,3323,3329,3331,3343,3347,3359,3361,3371,3373,3389,3391,3407,3413,3433,3449,3457,3461,3463,3467,3469,3491,3499,3511,3517,3527,3529,3533,3539,3541,3547,3557,3559,3571,3581,3583,3593,3607,3613,3617,3623,3631,3637,3643,3659,3671,3673,3677,3691,3697,3701,3709,3719,3727,3733,3739,3761,3767,3769,3779,3793,3797,3803,3821,3823,3833,3847,3851,3853,3863,3877,3881,3889,3907,3911,3917,3919,3923,3929,3931,3943,3947,3967,3989,4001,4003,4007,4013,4019,4021,4027,4049,4051,4057,4073,4079,4091,4093,4099,4111,4127,4129,4133,4139,4153,4157,4159,4177,4201,4211,4217,4219,4229,4231,4241,4243,4253,4259,4261,4271,4273,4283,4289,4297,4327,4337,4339,4349,4357,4363,4373,4391,4397,4409,4421,4423,4441,4447,4451,4457,4463,4481,4483,4493,4507,4513,4517,4519,4523,4547,4549,4561,4567,4583,4591,4597,4603,4621,4637,4639,4643,4649,4651,4657,4663,4673,4679,4691,4703,4721,4723,4729,4733,4751,4759,4783,4787,4789,4793,4799,4801,4813,4817,4831,4861,4871,4877,4889,4903,4909,4919,4931,4933,4937,4943,4951,4957,4967,4969,4973,4987,4993,4999,5003,5009,5011,5021,5023,5039,5051,5059,5077,5081,5087,5099,5101,5107,5113,5119,5147,5153,5167,5171,5179,5189,5197,5209,5227,5231,5233,5237,5261,5273,5279,5281,5297,5303,5309,5323,5333,5347,5351,5381,5387,5393,5399,5407,5413,5417,5419,5431,5437,5441,5443,5449,5471,5477,5479,5483,5501,5503,5507,5519,5521,5527,5531,5557,5563,5569,5573,5581,5591,5623,5639,5641,5647,5651,5653,5657,5659,5669,5683,5689,5693,5701,5711,5717,5737,5741,5743,5749,5779,5783,5791,5801,5807,5813,5821,5827,5839,5843,5849,5851,5857,5861,5867,5869,5879,5881,5897,5903,5923,5927,5939,5953,5981,5987,6007,6011,6029,6037,6043,6047,6053,6067,6073,6079,6089,6091,6101,6113,6121,6131,6133,6143,6151,6163,6173,6197,6199,6203,6211,6217,6221,6229,6247,6257,6263,6269,6271,6277,6287,6299,6301,6311,6317,6323,6329,6337,6343,6353,6359,6361,6367,6373,6379,6389,6397,6421,6427,6449,6451,6469,6473,6481,6491,6521,6529,6547,6551,6553,6563,6569,6571,6577,6581,6599,6607,6619,6637,6653,6659,6661,6673,6679,6689,6691,6701,6703,6709,6719,6733,6737,6761,6763,6779,6781,6791,6793,6803,6823,6827,6829,6833,6841,6857,6863,6869,6871,6883,6899,6907,6911,6917,6947,6949,6959,6961,6967,6971,6977,6983,6991,6997,7001,7013,7019,7027,7039,7043,7057,7069,7079,7103,7109,7121,7127,7129,7151,7159,7177,7187,7193,7207,7211,7213,7219,7229,7237,7243,7247,7253,7283,7297,7307,7309,7321,7331,7333,7349,7351,7369,7393,7411,7417,7433,7451,7457,7459,7477,7481,7487,7489,7499,7507,7517,7523,7529,7537,7541,7547,7549,7559,7561,7573,7577,7583,7589,7591,7603,7607,7621,7639,7643,7649,7669,7673,7681,7687,7691,7699,7703,7717,7723,7727,7741,7753,7757,7759,7789,7793,7817,7823,7829,7841,7853,7867,7873,7877,7879,7883,7901,7907,7919]

Άσκηση H3E2 Εγκαταστήστε τη βιβλιοθήκη HUnit με το cabal. Γράψτε κώδικα που να δημιουργεί στο κατάλληλο αρχείο τις συναρτήσεις έτσι ώστε τα unit tests του H3e2Test.hs που ακολουθεί να περνάνε.

Unit tests

import H3e2
import Test.HUnit

tests :: Test
tests =
  TestList
    [ 
        "rectangle"  ~: rectangle 2 5 ~?= 10,
        "power"  ~: power 2 10 ~?= 1024,
        "sumList"  ~: sumList [1,2,3,4,5] ~?= 15,
        "isPrime 57"  ~: isPrime 57 ~?= False,
        "isPrime 101"  ~: isPrime 101 ~?= True
    ]

main :: IO ()
main = do
  _ <- runTestTT tests
  return ()

Λύση άσκησης H3E2

Εγκατάσταση της βιβλιοθήκης HUnit:

$ cabal install --lib HUnit

Αρχείο με συναρτήσεις για τους ελέγχους:

module H3e2 where

-- Υπολογισμός εμβαδού ορθογωνίου
rectangle :: (Num a) => a -> a -> a
rectangle h w = h * w

-- Ύψωση ακεραίου σε μη αρνητική ακέραια δύναμη
power :: Int -> Int -> Int
power _ 0 = 1
power x n = x * power x (n - 1)

-- Άθροισμα στοιχείων λίστας
sumList :: [Int] -> Int
sumList [] = 0
sumList (x:xs) = x + sumList xs 

-- Έλεγχος αν ένας ακέραιος είναι πρώτος
isPrime :: Int -> Bool
isPrime n
  | n <= 1    = False
  | otherwise = not (any (\x -> n `mod` x == 0) [2..(n-1)])

Εκτέλεση ελέγχων:

$ runghc H3e2Test.hs
Cases: 5  Tried: 5  Errors: 0  Failures: 0

Άσκηση Η3Ε3 Στο άρθρο Implementing Unsure Calculator in 100 lines of Haskell παρουσιάζεται μια υλοποίηση σε μόλις 100 γραμμές κώδικα του unsure calculator. Φορτώστε τον κώδικα Haskell και εκτελέστε τα παραδείγματα εκφράσεων του άρθρου.