Tutorial by Examples: re

The easiest way to create a custom data type in Haskell is to use the data keyword: data Foo = Bar | Biz The name of the type is specified between data and =, and is called a type constructor. After = we specify all value constructors of our data type, delimited by the | sign. There is a rule in...

Value constructors are functions that return a value of a data type. Because of this, just like any other function, they can take one or more parameters: data Foo = Bar String Int | Biz String Let's check the type of the Bar value constructor. :t Bar prints Bar :: String -> Int -> Foo...

Type constructors can take one or more type parameters: data Foo a b = Bar a b | Biz a b Type parameters in Haskell must begin with a lowercase letter. Our custom data type is not a real type yet. In order to create values of our type, we must substitute all type parameters with actual types. Be...

A lot of Vim users find the Esc too hard to reach, and end up finding another mapping that's easy to reach from the home row. Note that Ctrl-[ may be equivalent to Esc on an English keyboard, and is much easier to reach. jk inoremap jk <ESC> This one is really easy to trigger; just smash...

IPv4 To match IPv4 address format, you need to check for numbers [0-9]{1,3} three times {3} separated by periods \. and ending with another number. ^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$ This regular expression is too simple - if you want to it to be accurate, you need to check that the numbers are be...

This is the normal HTML table structure <style> table { width: 100%; } </style> <table> <tr> <td> I'm a table </td> </tr> </table> You can do same implementation like this <style> .table-...

A Stopwatch instance can measure elapsed time over several intervals with the total elapsed time being all individual intervals added together. This gives a reliable method of measuring elapsed time between two or more events. Stopwatch stopWatch = new Stopwatch(); stopWatch.Start(); double d =...

Redux is very functional, so unit testing is very straightforward. Action creator: export function showSidebar () { return { type: 'SHOW_SIDEBAR' } } Action creators unit test: import expect from 'expect' import actions from './actions' import * as type from './constants' desc...

This is an example of something that would have been straight up impossible with labels. If you execute the same label multiple times at the same time and they rely on variables that are being defined within them, they very likely interfere and cause unexpected behavior. Here is how to do it with f...

The ref keyword is used to pass an Argument as Reference. out will do the same as ref but it does not require an assigned value by the caller prior to calling the function. Ref Parameter :-If you want to pass a variable as ref parameter then you need to initialize it before you pass it as ref param...

Assume we want to create a data type Person, which has a first and last name, an age, a phone number, a street, a zip code and a town. We could write data Person = Person String String Int Int String String String If we want now to get the phone number, we need to make a function getPhone :: P...

This error occurs when tables are not adequately structured to handle the speedy lookup verification of Foreign Key (FK) requirements that the developer is mandating. CREATE TABLE `gtType` ( `type` char(2) NOT NULL, `description` varchar(1000) NOT NULL, PRIMARY KEY (`type`) ) ENGINE=InnoD...

While server side-code can run with elevated privileges, there is not an equivalent method to elevate privileges in client-side code (for obvious security reasons). As an alternative, you can specify credentials to emulate the access of a specific user or service account. To specify credentials, bu...

Check existing remote git remote -v # origin https://github.com/username/repo.git (fetch) # origin https://github.com/usernam/repo.git (push) Changing repository URL git remote set-url origin https://github.com/username/repo2.git # Change the 'origin' remote's URL Verify new remote URL ...

Function TestFunction() As TestClass Return Nothing End Function BAD CODE TestFunction().TestMethod() GOOD CODE Dim x = TestFunction() If x IsNot Nothing Then x.TestMethod() 14.0 Null Conditional Operator TestFunction()?.TestMethod()

My.Computer.Network.DownloadFile("ftp://srv.my/myfile.txt", "donwload.txt", "Peter", "1234") This command download myfile.txt file from server named srv.my and saves it as donwload.txt into working directory. You can specify absolute path for downloaded fil...

My.Computer.Network.UploadFile("doc.txt", "ftp://server.my/on_server.txt", "Peter", "1234") This command upload doc.txt file from working directory (you could specify absolute path if you want) to server named server.my. File stored on the server will be na...

This example is inspired by this question. We'll assume you know how to load a file using the File API. // preliminary code to handle getting local file and finally printing to console // the results of our function ArrayBufferToBinary(). var file = // get handle to local file. var reader = new...

Structure for Binary Search Tree (BST) nodes: struct node { int data; node * left; node * right; } Search Algorithm // Check if a value exists in the tree bool BSTSearch(node * current, int value) { if (current->data == value) { return true; } e...

--dataset schemas must be identical SELECT 'Data1' as 'Column' UNION ALL SELECT 'Data2' as 'Column' UNION ALL SELECT 'Data3' as 'Column' UNION ALL SELECT 'Data4' as 'Column' UNION ALL SELECT 'Data5' as 'Column' EXCEPT SELECT 'Data3' as 'Column' --Returns Data1, Data2, Data4, and Data5