Tutorial by Examples: s

You can also update data in a table based on data from another table: UPDATE person SET state_code = cities.state_code FROM cities WHERE cities.city = city; Here we are joining the person city column to the cities city column in order to get the city's state code. This is then used to updat...

Everything in .NET is an object, hence every type has ToString() method defined in Object class which can be overridden. Default implementation of this method just returns the name of the type: public class Foo { } var foo = new Foo(); Console.WriteLine(foo); // outputs Foo ToString() is i...

Strings are immutable. You just cannot change existing string. Any operation on the string crates a new instance of the string having new value. It means that if you need to replace a single character in a very long string, memory will be allocated for a new value. string veryLongString = ... // m...

Despite String is a reference type == operator compares string values rather than references. As you may know string is just an array of characters. But if you think that strings equality check and comparison is made character by character, you are mistaken. This operation is culture specific (see ...

Using GNU grep grep -r 'pattern' <directory path> To also list line numbers of matches use -n option grep -rn 'pattern' <directory path> To search only files with particular glob pattern grep --include='*.txt' -r 'pattern' <directory path> Exclude file patterns or direc...

Say we are working on a class representing a Person by their first and last names. We have created a basic class to do this and implemented proper equals and hashCode methods. public class Person { private final String lastName; //invariant - nonnull private final String firstName; //in...

The Comparable<T> interface requires one method: public interface Comparable<T> { public int compareTo(T other); } And the Comparator<T> interface requires one method: public interface Comparator<T> { public int compare(T t1, T t2); } These two met...

Variables declared inside a function only exist (unless passed) inside that function. x <- 1 foo <- function(x) { y <- 3 z <- x + y return(z) } y Error: object 'y' not found Variables passed into a function and then reassigned are overwritten, but only insi...

Functions called within a function (ie subfunctions) must be defined within that function to access any variables defined in the local environment without being passed. This fails: bar <- function() { z <- x + y return(z) } foo <- function() { y <- 3 z <-...

Variables can be assigned globally from any environment using <<-. bar() can now access y. bar <- function() { z <- x + y return(z) } foo <- function() { y <<- 3 z <- bar() return(z) } foo() 4 Global assignment is highly discourag...

Environments in R can be explicitly call and named. Variables can be explicitly assigned and call to or from those environments. A commonly created environment is one which encloses package:base or a subenvironment within package:base. e1 <- new.env(parent = baseenv()) e2 <- new.env(parent ...

Functions and objects in different packages may have the same name. The package loaded later will 'mask' the earlier package and a warning message will be printed. When calling the function by name, the function from the most recently loaded package will be run. The earlier function can be accessed ...

Microsoft.CodeAnalysis.CSharp.Scripting.CSharpScript is a new C# script engine. var code = "(1 + 2).ToString()"; var run = await CSharpScript.RunAsync(code, ScriptOptions.Default); var result = (string)run.ReturnValue; Console.WriteLine(result); //output 3 You can compile and run an...

Microsoft.CSharp.CSharpCodeProvider can be used to compile C# classes. var code = @" public class Abc { public string Get() { return ""abc""; } } "; var options = new CompilerParameters(); options.GenerateExecutable = false; options.GenerateInMe...

A module is a single Python file that can be imported. Using a module looks like this: module.py def hi(): print("Hello world!") my_script.py import module module.hi() in an interpreter >>> from module import hi >>> hi() # Hello world!

A package is made up of multiple Python files (or modules), and can even include libraries written in C or C++. Instead of being a single file, it is an entire folder structure which might look like this: Folder package __init__.py dog.py hi.py __init__.py from package.dog import woof fro...

This example shows how Stopwatch can be used to benchmark a block of code. using System; using System.Diagnostics; public class Benchmark : IDisposable { private Stopwatch sw; public Benchmark() { sw = Stopwatch.StartNew(); } public voi...

C-style bit-manipulation x = -1; // -1 == 1111 1111 ... 1111b (See here for an explanation of why this works and is actually the best approach.) Using std::bitset std::bitset<10> x; x.set(); // Sets all bits to '1'

Programming in general often requires a decision or a branch within the code to account for how the code operates under different inputs or conditions. Within the C# programming language (and most programming languages for this matter), the simplest and sometimes the most useful way of creating a br...

Following on from the If-Else Statement example, it is now time to introduce the Else If statement. The Else If statement follows directly after the If statement in the If-Else If-Else structure, but intrinsically has has a similar syntax as the If statement. It is used to add more branches to the c...