Path to mathematics (2)-four major artifacts-Haskell (28)

24. Data. Set

Set is between list and ing. All elements are unique.

Fromlist constructs the set.

Prelude data. Set> Let X = data. Set. fromlist [11,22, 33,44

Prelude data. Set> let y = data. Set. fromlist [91,32, 33,44, 55]

Prelude data. Set>

Intersection

Prelude data. Set> intersection X Y

Fromlist [33,44, 55]

Prelude data. Set>

Difference removes some elements from the first set. These elements are handed over to the second set.

Prelude data. Set> data. Set. Difference X Y

Fromlist [11, 22]

Prelude data. Set>

Union completes the union of two sets

Prelude data. Set> data. Set. Union X Y

Fromlist [11, 22, 32, 33, 44,55, 91]

Prelude data. Set>

Null, size, Member, empty, Singleton, insert, and delete are similar to map operations.

25. definition module

We create a module for some functions defined in previous exercises:

We define two modules: mymodule. Test2 and mymodule. test1.

First, create two Program Files: test1.hs and test2.hs.

Test1.hs content:

Module mymodule. test1

(Mylength

, Oddcount

, Evencount

, Mysum

) Where

--------------

Mylength rows = sum [1 | _ <-rows]

Oddcount Limit = sum [1 | x <-limit, X 'mod' 2/= 0]

Evencount percent = sum [1 | x <-percent, even X]

-------------

Mysum: (integral a) => A->

Mysum 0 = 0

Mysum n = N + mysum (n-1)

Test2.hs content:

Module mymodule. Test2

(Myfst

, Mycnt

, Mylst

, Mymin

) Where

------------------

Myfst: (A, B, C)->

Mycnt: :( a, B, c)-> B

Mylst: (A, B, C)-> C

Myfst (A, _, _) =

Mycnt (_, B, _) = B

Mylst (_, _, c) = C

----------------------

Mymin: :( ord a) => [a]->

Mymin [] = error "empty list! "

Mymin [x] = x

Mymin (X: XS)

| X <minval = x

| Otherwise = minval

Where minval = mymin XS

Place the two files under the mymodule subdirectory of the program execution directory that requires the two modules. Then write a program to load the two modules and call the functions

Import mymodule. test1

Import mymodule. Test2

Test1_1 A = mylength

Test1_2 A = evencount

Test2_1 A = mycnt

Test2_2 A = mymin

Run the test:

* Main>: Load "mytestm. Hs"

[1 of 3] compiling mymodule. Test2 (mymodule \ test2.hs, interpreted)

[2 of 3] compiling mymodule. test1 (mymodule \ test1.hs, interpreted)

[3 of 3] compiling main (mytestm. Hs, interpreted)

OK, modules loaded: mymodule. test1, mymodule. Test2, Main.

* Main> test1_1 [11,22, 33]

3

* Main> test1_2 [11,22, 33]

1

* Main> test2_2 [11,22, 33]

11

* Main> test2_1 (11,22, 33)

22

* Main>

 

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