takes the head of a list-like object or uses the given default value

see ConsT for other supported types eg Seq

>>> pz @(HeadDef 444 Id) []
Val 444

>>> pz @(HeadDef 444 Id) [1..5]
Val 1

>>> pz @(HeadDef 444 Id) [1..5]
Val 1

>>> pz @(HeadDef (C "w") Id) (Seq.fromList "abcdef")
Val 'a'

>>> pz @(HeadDef (C "w") Id) Seq.empty
Val 'w'

>>> pz @(HeadDef (MEmptyT _) Id) ([] :: [SG.Sum Int])
Val (Sum {getSum = 0})

>>> pz @(HeadDef (MEmptyT String) '["abc","def","asdfadf"]) ()
Val "abc"

>>> pz @(HeadDef (MEmptyT _) Snd) (123,["abc","def","asdfadf"])
Val "abc"

>>> pz @(HeadDef (MEmptyT _) Snd) (123,[])
Val ()

>>> pl @(HeadDef 9 Fst) ([],True)
Present 9 (JustDef Nothing)
Val 9

>>> pl @(HeadDef 99 Fst) ([10..15],True)
Present 10 (JustDef Just)
Val 10

>>> pl @(HeadDef 12 Fst >> Le 6) ([],True)
False ((>>) False | {12 <= 6})
Val False

>>> pl @(HeadDef 1 Fst >> Le 6) ([],True)
True ((>>) True | {1 <= 6})
Val True

>>> pl @(HeadDef 10 Fst >> Le 6) ([],True)
False ((>>) False | {10 <= 6})
Val False

>>> pl @(HeadDef (MEmptyT _) Id) (map (:[]) ([] :: [Int]))
Present [] (JustDef Nothing)
Val []

>>> pl @(HeadDef (MEmptyT _) Id) (map (:[]) ([10..14] :: [Int]))
Present [10] (JustDef Just)
Val [10]

>>> pl @(HeadDef Fst Snd) (99,[10..14])
Present 10 (JustDef Just)
Val 10

>>> pl @(HeadDef Fst Snd) (99,[] :: [Int])
Present 99 (JustDef Nothing)
Val 99

>>> pl @(HeadDef 43 Snd) (99,[] :: [Int])
Present 43 (JustDef Nothing)
Val 43

takes the head of a list or fails with the given message

see ConsT for other supported types eg Seq

>>> pz @(HeadFail "oops" Id) ["abc","def","asdfadf"]
Val "abc"

>>> pz @(HeadFail "empty list" Id) []
Fail "empty list"

>>> pl @(HeadFail "zz" Fst >> Le 6) ([],True)
Error zz (JustFail Nothing)
Fail "zz"

>>> pl @((HeadFail "failed1" Fst >> Le 6) || 'False) ([],True)
Error failed1 (JustFail Nothing | ||)
Fail "failed1"

>>> pl @((Fst >> HeadFail "failed2" Id >> Le (6 -% 1)) || 'False) ([-9],True)
True (True || False)
Val True

>>> pl @(HeadFail "Asdf" Id) ([] :: [()]) -- breaks otherwise
Error Asdf (JustFail Nothing)
Fail "Asdf"

>>> pl @(HeadFail (PrintF "msg=%s def" Fst) Snd) ("Abc",[])
Error msg=Abc def (JustFail Nothing)
Fail "msg=Abc def"

takes the tail of a list-like object or uses the given default value

>>> pl @(TailDef '[9,7] Fst) ([],True)
Present [9,7] (JustDef Nothing)
Val [9,7]

>>> pl @(TailDef '[9,7] Fst) ([1..5],True)
Present [2,3,4,5] (JustDef Just)
Val [2,3,4,5]

>>> pl @(TailDef '[3] Fst) ([10..15],True)
Present [11,12,13,14,15] (JustDef Just)
Val [11,12,13,14,15]

takes the tail of a list-like object or fails with the given message

>>> pl @(TailFail (PrintT "a=%d b=%s" Snd) Fst) ([]::[()],(4,"someval"))
Error a=4 b=someval (JustFail Nothing)
Fail "a=4 b=someval"

takes the last value of a list-like object or a default value

>>> pl @(LastDef 9 Fst) ([],True)
Present 9 (JustDef Nothing)
Val 9

>>> pl @(LastDef 9 Fst) ([1..5],True)
Present 5 (JustDef Just)
Val 5

>>> pl @(LastDef 3 Fst) ([10..15],True)
Present 15 (JustDef Just)
Val 15

>>> pl @(LastDef 0 Id) [1..12]
Present 12 (JustDef Just)
Val 12

>>> pl @(LastDef 0 Id) []
Present 0 (JustDef Nothing)
Val 0

takes the init of a list-like object or fails with the given message

takes the init of a list-like object or uses the given default value

>>> pl @(InitDef '[9,7] Fst) ([],True)
Present [9,7] (JustDef Nothing)
Val [9,7]

>>> pl @(InitDef '[9,7] Fst) ([1..5],True)
Present [1,2,3,4] (JustDef Just)
Val [1,2,3,4]

>>> pl @(InitDef '[3] Fst) ([10..15],True)
Present [10,11,12,13,14] (JustDef Just)
Val [10,11,12,13,14]

takes the init of a list-like object or fails with the given message

similar to headMay

>>> pl @HeadMay []
Present Nothing ((>>) Nothing | {FMap <skipped>})
Val Nothing

>>> pl @HeadMay [99,7,3]
Present Just 99 ((>>) Just 99 | {FMap Fst 99 | (99,[7,3])})
Val (Just 99)

similar to lastMay

>>> pz @LastMay "hello"
Val (Just 'o')

similar to tailMay

>>> pz @TailMay "hello"
Val (Just "ello")

similar to initMay

>>> pz @InitMay "hello"
Val (Just "hell")

experimental: sorts then partitions and then sorts each partitions based on the leftmost occurring value in the original list if the existing order of data is fine then use GroupBy as you do not need this

>>> pz @(PartitionsBy (Fst ==! Snd) (L11 == L21) Id) [10,9,9,1,9]
Val [[10],[9,9,9],[1]]

>>> pz @(PartitionsBy OrdA (L11 < L21) Id) "efaffabec"
Val ["a","f","f","abce","ef"]

>>> pz @(PartitionsBy 'GT 'True Id) "efaffabec"
Val ["cebaffafe"]

>>> pz @(PartitionsBy 'GT 'False Id) "efaffabec"
Val ["e","f","a","f","f","a","b","e","c"]

>>> pz @(PartitionsBy (Fst ==! Snd) (L12 > L22) Id) [10,9,9,1,9,4]
Val [[9],[1],[9,10],[4,9]]

>>> pz @(PartitionsBy (L11 ==! L21) (L12 > L22) Id) "eddadc"
Val ["d","a","de","cd"]

>>> pz @(PartitionsBy (L11 ==! L21) (L11 < L21) Id) [10,9,9,1,9,4]
Val [[9],[1,4,9],[9,10]]

add an index to map

>>> pz @(Rescan "^(\\d+)\\.(\\d+)\\.(\\d+)\\.(\\d+)$" >> Map (Snd >> IMap (GuardBool (PrintT "bad value=%d %s" Id) (Snd >> ReadP Int Id < 255)) Id)) "123.222.999.3"
Fail "bad value=2 999"

>>> pz @(Rescan "^(\\d+)\\.(\\d+)\\.(\\d+)\\.(\\d+)$" >> Map (Snd >> IMap (GuardBool (PrintT "bad value=%d %s" Id) (Snd >> ReadP Int Id < 255)) Id)) "123.222.99.3"
Val [[True,True,True,True]]

add an index to list

>>> pz @IList "abcdef"
Val [(0,'a'),(1,'b'),(2,'c'),(3,'d'),(4,'e'),(5,'f')]

a predicate on prime numbers

>>> pz @IsPrime 2
Val True

>>> pz @(Map '(Id,IsPrime)) [0..12]
Val [(0,False),(1,False),(2,True),(3,True),(4,False),(5,True),(6,False),(7,True),(8,False),(9,False),(10,False),(11,True),(12,False)]

get the next prime number

>>> pz @PrimeNext 6
Val 7

>>> pz @(ScanN 4 PrimeNext Id) 3
Val [3,5,7,11,13]

get the next prime number

>>> pz @PrimePrev 6
Val 5

>>> pz @PrimePrev 5
Val 3

>>> pz @PrimePrev (-206)
Val 2

>>> pz @(ScanN 6 PrimePrev Id) 11
Val [11,7,5,3,2,2,2]

prime factorisation of positive numbers

>>> pz @(PrimeFactors Id) 17
Val [17]

>>> pz @(PrimeFactors Id) 1
Val [1]

>>> pz @(PrimeFactors Id) 30
Val [2,3,5]

>>> pz @(PrimeFactors Id) 64
Val [2,2,2,2,2,2]

>>> pz @(PrimeFactors Id) (-30)
Fail "PrimeFactors number<=0"

get list of n primes

>>> pz @(Primes Id) 5
Val [2,3,5,7,11]

IsLuhn predicate check on last digit

>>> pz @IsLuhn [1,2,3,0]
Val True

>>> pz @IsLuhn [1,2,3,4]
Val False

>>> pz @(GuardSimple IsLuhn) [15,4,3,1,99]
Fail "(IsLuhn map=[90,2,3,8,6] sum=109 ret=9 | [15,4,3,1,99])"

>>> pl @IsLuhn [15,4,3,1,99]
False (IsLuhn map=[90,2,3,8,6] sum=109 ret=9 | [15,4,3,1,99])
Val False