Relación 1

chapter {* R1: Programación funcional en Isabelle *}

theory R1_Programacion_funcional_en_Isabelle
imports Main 
begin

text {* ----------------------------------------------------------------
  Ejercicio 1. Definir, por recursión, la función
     longitud :: 'a list ⇒ nat
  tal que (longitud xs) es la longitud de la listas xs. Por ejemplo,
     longitud [a,b,c] = 3
  ------------------------------------------------------------------- *}

(* cammonagu pabalagon raffergon2*)
fun longitud :: "'a list ⇒ nat" where
  "longitud [] = 0 "
| "longitud (x#xs) = 1 + longitud xs "
2
value "longitud [a,b,c] = 3"

{* juacanrod *}
fun longitud2 :: "'a list ⇒ nat" where
  "longitud2 [] = 0" |
  "longitud2 (x#xs) = 1 + longitud2(xs)"

(* josgomrom4 *)
fun longitud3 :: "'a list ⇒ nat" where
  "longitud3 [] = 0" |
  "longitud3 x = 1 + longitud3 (tl x)"

text {* --------------------------------------------------------------- 
  Ejercicio 2. Definir la función
     fun intercambia :: 'a × 'b ⇒ 'b × 'a
  tal que (intercambia p) es el par obtenido intercambiando las
  componentes del par p. Por ejemplo,
     intercambia (u,v) = (v,u)
  ------------------------------------------------------------------ *}

(* pabalagon cammonagu raffergon2*)

fun intercambia :: "'a × 'b ⇒ 'b × 'a" where
  "intercambia (x,y) = (y, x)"

value "intercambia (u,v) = (v,u)"

{* juacanrod *}
fun intercambia2 :: "'a × 'b ⇒ 'b × 'a" where
  "intercambia2 (x,y) = (y, x)"

value "intercambia2 (u,v) = (v,u)"

text {* ---------------------------------------------------------------
  Ejercicio 3. Definir, por recursión, la función
     inversa :: 'a list ⇒ 'a list
  tal que (inversa xs) es la lista obtenida invirtiendo el orden de los
  elementos de xs. Por ejemplo,
     inversa [a,d,c] = [c,d,a]
  ------------------------------------------------------------------ *}

(* pabalagon *)

fun aux :: "'a list ⇒ 'a list ⇒ 'a list" where
  "aux [] a = a" |
  "aux (x#xs) a = aux xs (x#a)"

fun inversa :: "'a list ⇒ 'a list" where
  "inversa xs = aux xs []"

(* pabalagon raffergon2 cammonagu *)

fun inversa2 :: "'a list ⇒ 'a list" where
  "inversa2 [] = []" |
  "inversa2 (x#xs) = inversa2 xs @ [x]"

value "inversa [a,d,c] = [c,d,a]"
value "inversa2 [a,d,c] = [c,d,a]"

{* juacanrod *}
fun inversa3 :: "'a list ⇒ 'a list" where
  "inversa3 [] = []" |
  "inversa3 (xs) = inversa3(tl xs) @ [ hd (xs)]"

value "inversa3 [a,d,c] = [c,d,a]"

text {* --------------------------------------------------------------- 
  Ejercicio 4. Definir la función
     repite :: nat ⇒ 'a ⇒ 'a list
  tal que (repite n x) es la lista formada por n copias del elemento
  x. Por ejemplo, 
     repite 3 a = [a,a,a]
  ------------------------------------------------------------------ *}

(* pabalagon *)

fun repite :: "nat ⇒ 'a ⇒ 'a list" where
  "repite 0 x = []"
| "repite (Suc n) x = x # repite n x"


(* raffergon2 cammonagu*)
fun repite2 :: "nat ⇒ 'a ⇒ 'a list" where
  "repite2 0 x = [] "
| "repite2 n x = x # repite2 (n-1) x "

value "repite 3 a = [a,a,a]"
value "repite2 3 a = [a,a,a]"

{* juacanrod *}
fun repite3 :: "nat ⇒ 'a ⇒ 'a list" where
  "repite3 0 a = []" |
  "repite3 n a = [a] @ repite3 (n-1) a" 
  
value "repite3 3 a = [a,a,a]"


text {* --------------------------------------------------------------- 
  Ejercicio 5. Definir la función
     conc :: 'a list ⇒ 'a list ⇒ 'a list
  tal que (conc xs ys) es la concatención de las listas xs e ys. Por
  ejemplo, 
     conc [a,d] [b,d,a,c] = [a,d,b,d,a,c]
  ------------------------------------------------------------------ *}

(* pabalagon raffergon2 *)

fun conc :: "'a list ⇒ 'a list ⇒ 'a list" where
  "conc [] ys = ys" |
  "conc (x#xs) ys = x # conc xs ys"

(* cammonagu *)
fun conc2 :: "'a list ⇒ 'a list ⇒ 'a list" where
  "conc2  ys [] = ys" |
  "conc2 xs (y#ys) =    xs @y # ys"

value "conc [a,d] [b,d,a,c] = [a,d,b,d,a,c]"
value "conc2 [a,d] [b,d,a,c] = [a,d,b,d,a,c]"


{* juacanrod *}
fun conc3 :: "'a list ⇒ 'a list ⇒ 'a list" where
  "conc3 [] ys = ys" |
  "conc3 xs ys = [hd (xs)] @ conc3 (tl (xs)) ys"

value "conc3 [a,d] [b,d,a,c] = [a,d,b,d,a,c]"

text {* --------------------------------------------------------------- 
  Ejercicio 6. Definir la función
     coge :: nat ⇒ 'a list ⇒ 'a list
  tal que (coge n xs) es la lista de los n primeros elementos de xs. Por 
  ejemplo, 
     coge 2 [a,c,d,b,e] = [a,c]
  ------------------------------------------------------------------ *}

(* pabalagon raffergon2 *)

fun coge :: "nat ⇒ 'a list ⇒ 'a list" where
  "coge 0 xs = []" |
  "coge n [] = []" |
  "coge (Suc n) (x#xs) = x # coge n xs"

(* cammonagu *)
fun coge2 :: "nat ⇒ 'a list ⇒ 'a list" where
  "coge2 0 xs = []" |
  "coge2 n [] = []" |
  "coge2 n (x#xs) = x # coge2 (n-1) xs"

value "coge 2 [a,c,d,b,e] = [a,c]"
value "coge2 2 [a,c,d,b,e] = [a,c]"

{* juacanrod *}
fun coge3 :: "nat ⇒ 'a list ⇒ 'a list" where
  "coge3 0 xs = []" |
  "coge3 n xs = [hd (xs)] @ coge3 (n-1) (tl (xs))" 

value "coge3 2 [a,c,d,b,e] = [a,c]"

text {* --------------------------------------------------------------- 
  Ejercicio 7. Definir la función
     elimina :: nat ⇒ 'a list ⇒ 'a list
  tal que (elimina n xs) es la lista obtenida eliminando los n primeros
  elementos de xs. Por ejemplo, 
     elimina 2 [a,c,d,b,e] = [d,b,e]
  ------------------------------------------------------------------ *}

(* pabalagon *)

fun elimina :: "nat ⇒ 'a list ⇒ 'a list" where
  "elimina 0 xs = []" |
  "elimina n [] = []" |
  "elimina (Suc n) (x#xs) = elimina n xs"

(* raffergon2 cammonagu *)

fun elimina2 :: "nat ⇒ 'a list ⇒ 'a list" where
  "elimina2 0 xs = xs" |
  "elimina2 n [] = []" |
  "elimina2 n (x#xs) = elimina2 (n-1) xs"

value "elimina 2 [a,c,d,b,e] = [d,b,e]"
value "elimina2 2 [a,c,d,b,e] = [d,b,e]"

{* juacanrod *}
fun elimina3 :: "nat ⇒ 'a list ⇒ 'a list" where
  "elimina3 0 xs = xs" |
  "elimina3 n xs = elimina3 (n-1) (tl xs)" 

value "elimina3 2 [a,c,d,b,e] = [d,b,e]"


text {* --------------------------------------------------------------- 
  Ejercicio 8. Definir la función
     esVacia :: 'a list ⇒ bool
  tal que (esVacia xs) se verifica si xs es la lista vacía. Por ejemplo,
     esVacia [a] = False
  ------------------------------------------------------------------ *}

(* pabalagon raffergon2*)

fun esVacia :: "'a list ⇒ bool" where
  "esVacia [] = True" |
  "esVacia xs = False"

(* cammonagu *)

fun esVacia2 :: "'a list ⇒ bool" where
  "esVacia2 xs = (longitud xs =0)" 
  

value "esVacia [a] = False"
value "esVacia2[a] = False"

{* juacanrod *}
fun esVacia3 :: "'a list ⇒ bool" where
  "esVacia3 xs = (length xs = 0)"

value "esVacia3 [a] = False"

text {* --------------------------------------------------------------- 
  Ejercicio 9. Definir la función
     inversaAc :: 'a list ⇒ 'a list
  tal que (inversaAc xs) es a inversa de xs calculada usando
  acumuladores. Por ejemplo, 
     inversaAc [a,c,b,e] = [e,b,c,a]
  ------------------------------------------------------------------ *}

(* pabalagon cammonagu*)

fun inversaAcAux :: "'a list ⇒ 'a list ⇒ 'a list" where
  "inversaAcAux [] ys = ys" |
  "inversaAcAux (x#xs) ys = inversaAcAux xs (x#ys)"

fun inversaAc :: "'a list ⇒ 'a list" where
  "inversaAc xs = inversaAcAux xs []"

value "inversaAc [a,c,b,e] = [e,b,c,a]"

{* juacanrod *}
fun inversaAcAux2 :: "'a list ⇒ 'a list ⇒ 'a list" where
  "inversaAcAux2 [] ys = ys" |
  "inversaAcAux2 xs ys = inversaAcAux2 (tl xs) ([hd xs]) @ ys"

value "inversaAcAux2 [a,b,c] []"

fun inversaAc2 :: "'a list ⇒ 'a list" where
  "inversaAc2 xs = inversaAcAux2 xs []"

value "inversaAc2 [a,c,b,e] = [e,b,c,a]"

text {* --------------------------------------------------------------- 
  Ejercicio 10. Definir la función
     sum :: nat list ⇒ nat
  tal que (sum xs) es la suma de los elementos de xs. Por ejemplo,
     sum [3,2,5] = 10
  ------------------------------------------------------------------ *}

(* pabalagon raffergon2*)

fun sum :: "nat list ⇒ nat" where
  "sum [] = 0" |
  "sum (x#xs) = x + sum xs"

(* cammonagu *)

fun sum2:: "nat list ⇒ nat" where
  "sum2 [] = 0" |
  "sum2 [x] = x" |
  "sum2 (x#xs) = x + sum xs"


value " sum [3,2,5] = 10"
value " sum2 [3,2,5] = 10"

{* juacanrod *}
fun sum3 :: "nat list ⇒ nat" where
  "sum3 [] = 0" |
  "sum3 xs = (hd xs) + sum3 (tl xs)"

value "sum3 [3,2,5,1]"


text {* --------------------------------------------------------------- 
  Ejercicio 11. Definir la función
     map :: ('a ⇒ 'b) ⇒ 'a list ⇒ 'b list
  tal que (map f xs) es la lista obtenida aplicando la función f a los
  elementos de xs. Por ejemplo,
     map (λx. 2*x) [3,2,5] = [6,4,10]
  ------------------------------------------------------------------ *}

(* pabalagon raffergon2 cammonagu*)

fun map :: "('a ⇒ 'b) ⇒ 'a list ⇒ 'b list" where
  "map f [] = []" |
  "map f (x#xs) = f x # map f xs"

{* juacanrod *}
fun map2 :: "('a ⇒ 'b) ⇒ 'a list ⇒ 'b list" where
  "map2 f [] = []" |
  "map2 f (x#xs) = [(f x)] @ map2 f xs"

value "map2 (λn. Suc n) [2,3,4,5]"


end