Día de la semana

Definir la función

   dia :: Int -> Int -> Int -> String

1	dia :: Int -> Int -> Int -> String

tal que (dia d m a) es el día de la semana correspondiente al día d del mes m del año a. Por ejemplo,

   dia 21 12 2016  ==  "Miercoles"
   dia 14  4 1936  ==  "Martes"

1 2	dia 21 12 2016 == "Miercoles" dia 14 4 1936 == "Martes"

Nota: Este ejercicio ha sido propuesto por Miguel Ibáñez.

Soluciones

-- 1ª solución
-- ===========

-- Comentario: usar que el 1-1-2007 cayó en lunes

dSem :: [(String,Int)]
dSem = [("Lunes",0),("Martes",1),("Miercoles",2),("Jueves",3),
        ("Viernes",4),("Sabado",5),("Domingo",6)]

dMes :: [(Int,Int)]
dMes = [(1,31),(2,28),(3,31),( 4,30),( 5,31),( 6,30),
        (7,31),(8,31),(9,30),(10,31),(11,30),(12,31)]

busca :: a -> [(a1,a2)] -> (a -> a1 -> Bool) -> [(a1,a2)]
busca x xs p  =  [(x',y) | (x',y) <- xs, p x x']

diaAno :: (Int,Int,Int) -> Int
diaAno (d,m,a)  =  d + sum [y | (x,y) <- busca m dMes (>)]

dia :: Int -> Int -> Int -> String
dia d m a = head [fst (x,y') | (x,y') <- dSem, n == y']
  where  n = mod ((diaAno (d,m,a) + (a - 2007)*365) + x) 7
         x | d <= 29 && m <= 2  =  div (a - 2007) 4 - 1
           | otherwise          =  div (a - 2007) 4


-- 2ª solución
-- ===========

-- Usando la congruencia de Zeller http://bit.ly/2gYxHym

dia2 :: Int -> Int -> Int -> String
dia2 d m a = diasSemana !! h
  where m1 = if   (m < 3)
             then m + 12
             else m

        a1 = if   (m1 > 12)
             then a - 1
             else a

        k  = a1 `mod` 100
        j  = a1 `div` 100

        h  = ( d
             + ((13 * (m1 + 1)) `div` 5)
             + k
             + (k `div` 4)
             + (j `div` 4)
             - (2 * j)
             ) `mod` 7

diasSemana :: [String]
diasSemana = [ "Sabado" 
             , "Domingo"
             , "Lunes" 
             , "Martes"
             , "Miercoles"
             , "Jueves"
             , "Viernes"]

-- 1ª solución

-- ===========

-- Comentario: usar que el 1-1-2007 cayó en lunes

dSem :: [(String,Int)]

dSem = [("Lunes",0),("Martes",1),("Miercoles",2),("Jueves",3),

("Viernes",4),("Sabado",5),("Domingo",6)]

dMes :: [(Int,Int)]

dMes = [(1,31),(2,28),(3,31),( 4,30),( 5,31),( 6,30),

(7,31),(8,31),(9,30),(10,31),(11,30),(12,31)]

busca :: a -> [(a1,a2)] -> (a -> a1 -> Bool) -> [(a1,a2)]

busca x xs p = [(x',y) | (x',y) <- xs, p x x']

diaAno :: (Int,Int,Int) -> Int

diaAno (d,m,a) = d + sum [y | (x,y) <- busca m dMes (>)]

dia :: Int -> Int -> Int -> String

dia d m a = head [fst (x,y') | (x,y') <- dSem, n == y']

where n = mod ((diaAno (d,m,a) + (a - 2007)*365) + x) 7

x | d <= 29 && m <= 2 = div (a - 2007) 4 - 1

| otherwise = div (a - 2007) 4

-- 2ª solución

-- ===========

-- Usando la congruencia de Zeller http://bit.ly/2gYxHym

dia2 :: Int -> Int -> Int -> String

dia2 d m a = diasSemana !! h

where m1 = if (m < 3)

then m + 12

else m

a1 = if (m1 > 12)

then a - 1

else a

k = a1 `mod` 100

j = a1 `div` 100

h = ( d

+ ((13 * (m1 + 1)) `div` 5)

+ k

+ (k `div` 4)

+ (j `div` 4)

- (2 * j)

) `mod` 7

diasSemana :: [String]

diasSemana = [ "Sabado"

, "Domingo"

, "Lunes"

, "Martes"

, "Miercoles"

, "Jueves"

, "Viernes"]

2 Comentarios

dia :: Int -> Int -> Int -> String
dia d m a = cp (mod (d-1 + mes a m + año a + 5) 7)
  where mes _ 1 = 0
        mes a m | m == 3 && bis a = 1 + mes a 2
                | m == 3 = mes a 2
                | elem m [2,4,6,8,9,11] = 3 + mes a (m-1)
                | otherwise = 2 + mes a (m-1)
        año a | a < 2016 = evP a
              | a == 2016 = 0
              | otherwise = evF a
        evP 2016 = 0
        evP a | bis a = evP (1+a) - 2
              | otherwise = evP (1+a) - 1
        evF 2016 = 0
        evF a | bis (a-1) = 2 + año (a-1)
              | otherwise = 1 + año (a-1)

cp x = head [ b | (a,b) <- lista, a == x]

lista = [ (1,"Lunes")
        , (2,"Martes")
        , (3,"Miercoles")
        , (4,"Jueves")
        , (5,"Viernes")
        , (6,"Sabado")
        , (0,"Domingo")]

bis a = (mod a 4 == 0)&&(not (mod a 100 == 0) || (mod a 400 == 0))

dia :: Int -> Int -> Int -> String

dia d m a = cp (mod (d-1 + mes a m + año a + 5) 7)

where mes _ 1 = 0

mes a m | m == 3 && bis a = 1 + mes a 2

| m == 3 = mes a 2

| elem m [2,4,6,8,9,11] = 3 + mes a (m-1)

| otherwise = 2 + mes a (m-1)

año a | a < 2016 = evP a

| a == 2016 = 0

| otherwise = evF a

evP 2016 = 0

evP a | bis a = evP (1+a) - 2

| otherwise = evP (1+a) - 1

evF 2016 = 0

evF a | bis (a-1) = 2 + año (a-1)

| otherwise = 1 + año (a-1)

cp x = head [ b | (a,b) <- lista, a == x]

lista = [ (1,"Lunes")

, (2,"Martes")

, (3,"Miercoles")

, (4,"Jueves")

, (5,"Viernes")

, (6,"Sabado")

, (0,"Domingo")]

bis a = (mod a 4 == 0)&&(not (mod a 100 == 0) || (mod a 400 == 0))

Responder

-- Por Congruencia de Zeller (https://es.wikipedia.org/wiki/Congruencia_de_Zeller)
dia :: Int -> Int -> Int -> String
dia d m a | m <= 2    = dia d (m+12) (a-1)
          | otherwise = dias!!(h `mod` 7)
  where (j,k) = a `divMod` 100
        h = d + (26*(m+1)) `div` 10 + k + k `div` 4 + j `div` 4 + 5*j
        dias = ["Sabado","Domingo","Lunes","Martes","Miercoles","Jueves","Viernes"]

-- Por Congruencia de Zeller (https://es.wikipedia.org/wiki/Congruencia_de_Zeller)

dia :: Int -> Int -> Int -> String

dia d m a | m <= 2 = dia d (m+12) (a-1)

| otherwise = dias!!(h `mod` 7)

where (j,k) = a `divMod` 100

h = d + (26*(m+1)) `div` 10 + k + k `div` 4 + j `div` 4 + 5*j

dias = ["Sabado","Domingo","Lunes","Martes","Miercoles","Jueves","Viernes"]

Responder

Día de la semana

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