An int p >= 2 is prime if and only if ((p-1)!+1)%p = 0 ((5-1)!+1)%5 4!+1 %5 24+1 %5 25 %5 0 PRIME (7-1)!+1 %7 6! + 1 %7 720+1 %7 721 %7 0 PRIME (6-1)!+1 %6 5! +1 %6 120 +1 %6 121 %6 1 NOT PRIME isprime 1 = False isprime n = length( filter (\x -> n `mod` x == 0) [2..(n-1)])==0 [2..(n-1)] is a list containing the ints from 2 to n-1. \x -> n `mod` x == 0 This is a function that mods n by x returning True if the mod is 0, meaning it returns True if n is divisible by x. Applying filter with this function does this: It tests every element in the list to see if its divisible by n and keeping those elements which are. Should 1 be prime? The world (except France) says no. Because of the Fundamental Theorem of Arithmetic. Every positive integer can be expressed uniquely as a product of primes. 15 = 3 x 5 15 = 3 x 5 x 1 15 = 3 x 5 x 1 x 1 If n is 6 We take the list [2,3,4,5] If we apply our lambda function to these elements, we get [True,True,False,False]. filter keeps the true ones, so we get [2,3]. The length of this list is 2, not 0, so 6 is not prime. If n is 5 The list is [2,3,4]. Applying our lambda gives us [False,False,False]. Applying the filter gives us []. Length is 0, so 5 is prime. A perfect number: the number is equal to the sum of the factors less than itself. Factors of 6 are 1, 2, and 3. 1+2+3 = 6. isperfect 1 = False isperfect n = foldl (+) 0 ( filter (\x -> n `mod` x == 0) [1..(n-1)])==n [1..(n-1)] is the list of all the numbers from 1 to n-1 The filter and the lambda give us the list of all factors, just like it does in the prime program. If n is 6, then the list is [1,2,3,4,5] Applying the function gives us [True,True,True,False,False]. The filter gives us [1,2,3]. The foldl gives 0+1+2+3 which is 6. We test whether that sum is equal to the original number. ghci> maxel n [] = [] The maxel function will return all the elements <= n in a list under the assumption that the list is nondecreasing. ghci> maxel n l = if ((head l) > n) then [] else (head l):(maxel n (tail l)) ghci> maxel 100 perfect [6,28] ghci> maxel 500 perfect [6,28,496] functions like map, filter, fold, zip...these handle 99% of the stuff you probably want to do with your lists (or information) anyway. You don't really need to use recursion much. (Or loops/tail recursion). Nearly everything you need to do can be handled with these methods, plus the notion of streams (or infinite lists). Remember LISP: What's the difference between mapcar and maplist in LISP? mapcar #'f (list a b c d e) gives us (list (f a) (f b) (f c) (f d) (f e)) maplist #'f (list a b c d e) gives us (list (f (list a b c d e)) (f (list b c d e)) (f (list c d e)) (f (list d e)) (f (list e))) maplist applies f to the sublists rather than just to the specific list element maplist is such a useful function ... but I can't find anything like it in Haskell. So, here's what I do in Haskell. ghci> lol l = if (length l)==0 then [] else l:lol (tail l) With lol you can create a list of sublists and then use map to apply on the list of sublists. So map f lol l in Haskell is roughly the same as maplist #'f l in Lisp. one of Haskell's advantages over Lisp is that it has an EASY way to make lists based on a single number, e.g. [1..n], which simply does not exist in LISP. Also streams, [1..] Except for 2 and 3 every prime is either one more or one less than a multiple of 6. 2,3,5,7,11,13,17,19 6n, 6n+1, 6n+2, 6n+3, 6n+4, 6n+5 N N N N C:\Users\apoe\Desktop>ghci GHCi, version 9.4.8: https://www.haskell.org/ghc/ :? for help ghci> :load "fns.hs" [1 of 2] Compiling Main ( fns.hs, interpreted ) Ok, one module loaded. ghci> isprime 17 True ghci> isprime 541 True ghci> isprime 121 False ghci> isprime 11111111 False ghci> primes = filter isprime [1..] ghci> primes [2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997,1009,1013,1019,1021,1031,1033,1039,1049,1051,1061,1063,1069,1087,1091,1093,1097,1103,1109,1117,1123,1129,1151,1153,1163,1171,1181,1187,1193,1201,1213,1217,1223,1229,1231,1237,1249,1259,1277,1279,1283,1289,1291,1297,1301,1303,1307,1319,1321,1327,1361,1367,1373,1381,1399,1409,1423,1427,1429,1433,1439,1447,1451,1453,1459,1471,1481,1483,1487,1489,1493,1499,1511,1523,1531,1543,1549,1553,1559,1567,1571,1579,1583,1597,1601,1607,1609,1613,1619,1621,1627,1637,1657,1663,1667,1669,1693,1697,1699,1709,1721,1723,1733,1741,1747,1753,1759,1777,1783,1787,1789,1801,1811,1823,1831,1847,1861,1867,1871,1873,1877,1879,1889,1901,1907,1913,1931,1933,1949,1951,1973,1979,1987,1993,1997,1999,2003,2011,2017,2027,2029,2039,2053,2063,2069,2081,2083,2087,2089,2099,2111,2113,2129,2131,2137,2141,2143,2153,2161,2179,2203,2207,2213,2221,2237,2239,2243,2251,2267,2269,2273,2281,2287,2293,2297,2309,2311,2333,2339,2341,2347,2351,2357,2371,2377,2381,2383,2389,2393,2399,2411,2417,2423,2437,2441,2447,2459,2467,2473,2477,2503,2521,2531,2539,2543,2549,2551,2557,2579,2591,2593,2609,2617,2621,2633,2647,2657,2659,2663,2671,2677,2683,2687,2689,2693,2699,2707,2711,2713,2719,2729,2731,2741,2749,2753,2767,2777,2789,2791,2797,2801,2803,2819,2833,2837,2843,2851,2857,2861,2879,2887,2897,2903,2909,2917,2927,2939,2953,2957,2963,2969,2971,2999,3001,3011,3019,3023,3037,3041,3049,3061,3067,3079,3083,3089,3109,3119,3121,3137,3163,3167,3169,3181,3187,3191,3203,3209,3217,3221,3229,3251,3253,3257,3259,3271,3299,3301,3307,3313,3319,3323,3329,3331,3343,3347,3359,3361,3371,3373,3389,3391,3407,3413,3433,3449,3457,3461,3463,3467,3469,3491,3499,3511,3517,3527,3529,3533,3539,3541,3547,3557,3559,3571,3581,3583,3593,3607,3613,3617,3623,3631,3637,3643,3659,3671,3673,3677,3691,3697,3701,3709,3719,3727,3733,3739,3761,3767,3769,3779,3793,3797,3803,3821,3823,3833,3847,3851,3853,3863,3877,3881,3889,3907,3911,3917,3919,3923,3929,3931,3943,3947,3967,3989,4001,4003,4007,4013,4019,4021,4027,4049,4051,4057,4073,4079,4091,4093,4099,4111,4127,4129,4133,4139,4153,4157,4159,4177,4201,4211,4217,4219,4229,4231,4241,4243,4253,4259,4261,4271,4273,4283,4289,4297,4327,4337,4339,4349,4357,4363,4373,4391,4397,4409,4421,4423,4441,4447,4451,4457,4463,4481,4483,4493,4507,4513,4517,4519,4523,4547,4549,4561,4567,4583,4591,4597,4603,4621,4637,4639,4643,4649,4651,4657,4663,4673,4679,4691,4703,4721,4723,4729,4733,4751,4759,4783,4787,4789,4793,4799,4801,4813,4817,4831,4861,4871,4877,4889,4903,4909,4919,4931,4933,4937,4943,4951,4957,4967,4969,4973,4987,4993,4999,5003,5009,5011,5021,5023,5039,5051,5059,5077,5081,5087,5099,5101,5107,5113,5119,5147,5153,5167,5171,5179,5189,5197,5209,5227,5231,5233,5237,5261,5273,5279,5281,5297,5303,5309,5323,5333,5347,5351,5381,5387,5393,5399,5407,5413,5417,5419,5431,5437,5441,5443,5449,5471,5477,5479,5483,5501,5503,5507,5519,5521,5527,5531,5557,5563,5569,5573,5581,5591,5623,5639,5641,5647,5651,5653,5657,5659,5669,5683,5689,5693,5701,5711,5717,5737,5741,5743,5749,5779,5783,5791,5801,5807,5813,5821,5827,5839,5843,5849,5851,5857,5861,5867,5869,5879,5881,5897,5903,5923,5927,5939,5953,5981,5987,6007,6011,6029,6037,6043,6047,6053,6067,6073,6079,6089,6091,6101,6113,6121,6131,6133,6143,6151,6163,6173,6197,6199,6203,6211,6217,6221,6229,6247,6257,6263,6269,6271,6277,6287,6299,6301,6311,6317,6323,6329,6337,6343,6353,6359,6361,6367,6373,6379,6389,6397,6421,6427,6449,6451,6469,6473,6481,6491,6521,6529,6547,6551,6553,6563,6569,6571,6577,6581,6599,6607,6619,6637,6653,6659,6661,6673,6679,6689,6691,6701,6703,6709,6719,6733,6737,6761,6763,6779,6781,6791,6793,6803Interrupted. ghci> take 100 primes [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] ghci> sqrt 5 2.23606797749979 ghci> [1..sqrt 5] [1.0,2.0] ghci> 1..int (sqrt 5) :11:2: error: parse error on input `..' ghci> ghci> [sqrt 5] [2.23606797749979] ghci> [1..round (sqrt 5)] [1,2] ghci> [1..round (sqrt 25)] [1,2,3,4,5] ghci> :load "fns.hs" [1 of 2] Compiling Main ( fns.hs, interpreted ) Ok, one module loaded. ghci> isprime 2 :17:1: error: * Ambiguous type variable `a0' arising from a use of `isprime' prevents the constraint `(Integral a0)' from being solved. Probable fix: use a type annotation to specify what `a0' should be. Potentially matching instances: instance Integral Integer -- Defined in `GHC.Real' instance Integral Int -- Defined in `GHC.Real' ...plus one other ...plus one instance involving out-of-scope types (use -fprint-potential-instances to see them all) * In the expression: isprime 2 In an equation for `it': it = isprime 2 :17:9: error: * Ambiguous type variable `a0' arising from the literal `2' prevents the constraint `(Num a0)' from being solved. Probable fix: use a type annotation to specify what `a0' should be. Potentially matching instances: instance Num Integer -- Defined in `GHC.Num' instance Num Double -- Defined in `GHC.Float' ...plus three others ...plus two instances involving out-of-scope types (use -fprint-potential-instances to see them all) * In the first argument of `isprime', namely `2' In the expression: isprime 2 In an equation for `it': it = isprime 2 ghci> [2..1] [] ghci> isprime 100 :19:1: error: * Ambiguous type variable `a0' arising from a use of `isprime' prevents the constraint `(Integral a0)' from being solved. Probable fix: use a type annotation to specify what `a0' should be. Potentially matching instances: instance Integral Integer -- Defined in `GHC.Real' instance Integral Int -- Defined in `GHC.Real' ...plus one other ...plus one instance involving out-of-scope types (use -fprint-potential-instances to see them all) * In the expression: isprime 100 In an equation for `it': it = isprime 100 :19:9: error: * Ambiguous type variable `a0' arising from the literal `100' prevents the constraint `(Num a0)' from being solved. Probable fix: use a type annotation to specify what `a0' should be. Potentially matching instances: instance Num Integer -- Defined in `GHC.Num' instance Num Double -- Defined in `GHC.Float' ...plus three others ...plus two instances involving out-of-scope types (use -fprint-potential-instances to see them all) * In the first argument of `isprime', namely `100' In the expression: isprime 100 In an equation for `it': it = isprime 100 ghci> :load "fns.h" target `fns.h' is not a module name or a source file ghci> :load "fns.hs" [1 of 2] Compiling Main ( fns.hs, interpreted ) Ok, one module loaded. ghci> isprime 100 False ghci> take 1000 primes :23:11: error: Variable not in scope: primes :: [a] ghci> primes = filter isprime [1..] ghci> take 1000 primes [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] ghci> isperfect 6 True ghci> isperfect 7 False ghci> isperfect 16777216 False ghci> perfect = filter isperfect [1..] ghci> perfect [6,28,496,8128Interrupted. ghci> ghci> take 3 perfect [6,28,496] ghci> take (<=100) perfect :33:7: error: * Couldn't match expected type `Int' with actual type `a0 -> Bool' * In the first argument of `take', namely `(<= 100)' In the expression: take (<= 100) perfect In an equation for `it': it = take (<= 100) perfect ghci> filter (<=100) perfect [6,28Interrupted. ghci> maxel n [] = [] ghci> maxel 100 [] [] ghci> maxel n l = if ((head l) > n) then [] else (head l):(maxel n (tail l)) ghci> maxel 100 perfect [6,28] ghci> maxel 500 perfect [6,28,496] ghci> maxel 500 perfect [6,28,496] ghci> take 12 primes [2,3,5,7,11,13,17,19,23,29,31,37] ghci> lol l = if (length l)==0 then [] else l:lol (tail l) ghci> lol [1..5] [[1,2,3,4,5],[2,3,4,5],[3,4,5],[4,5],[5]] ghci> lol (take 10 primes) [[2,3,5,7,11,13,17,19,23,29],[3,5,7,11,13,17,19,23,29],[5,7,11,13,17,19,23,29],[7,11,13,17,19,23,29],[11,13,17,19,23,29],[13,17,19,23,29],[17,19,23,29],[19,23,29],[23,29],[29]] ghci> primt :45:1: error: Variable not in scope: primt Suggested fix: Perhaps use `print' (imported from Prelude) ghci> primes [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,Interrupted. ghci> filter isprime [1..] [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,Interrupted. ghci> primes = 2:(filter isprime [1,3...]) :48:31: error: A section must be enclosed in parentheses thus: (3 ...) ghci> primes = 2:(filter isprime [1,3..]) ghci> take 10 primes [2,3,5,7,11,13,17,19,23,29] ghci> 2:3:[5] [2,3,5] ghci>