Tutorial by Examples: b

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...

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...

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 ...

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'

The following command imports CSV files into a MySQL table with the same columns while respecting CSV quoting and escaping rules. load data infile '/tmp/file.csv' into table my_table fields terminated by ',' optionally enclosed by '"' escaped by '"' lines terminated by '\n' ignore 1...

The awk language does not directly support variables local to functions. It is however easy emulate them by adding extra arguments to functions. It is traditional to prefix these variables by a _ to indicate that they are not actual parameters. We illustrate this technique with the definition of a...

// Returns the nth number in the Fibonacci sequence function fibonacci(n) { if (n === 1 || n === 0) { return 1; } else { return fibonacci(n - 1) + fibonacci(n - 2); } }

A cancelable event can be raised by a class when it is about to perform an action that can be canceled, such as the FormClosing event of a Form. To create such event: Create a new event arg deriving from CancelEventArgs and add additional properties for event data. Create an event using EventH...

#| We make block comments like this |#

One of the most useful queries for end users of large RDBMS's is a search of an information schema. Such a query allows users to rapidly find database tables containing columns of interest, such as when attempting to relate data from 2 tables indirectly through a third table, without existing knowl...

::This is a label that acts as a comment The double-colon :: comment shown above is not documented as being a comment command, but it is a special case of a label that acts as a comment. Caution: when labels are used as comments within a bracketed code block or for command, the command processor...

It is also possible to use variables as comments. This can be useful to conditionally prevent commands being executed: @echo off setlocal if /i "%~1"=="update" (set _skip=) Else (set _skip=REM) %_skip% copy update.dat %_skip% echo Update applied ... When using the ab...

The batch file format does not have a block comment syntax, but there is an easy workaround for this. Normally each line of a batch file is read and then executed by the parser, but a goto statement can be used to jump past a block of plain text (which can be used as a block comment): @echo off ...

Environment variables can be defined before the meteor call, like so: PORT=4000 meteor NODE_ENV="staging" meteor

Downloading a file from the internet is a very common task required by almost every application your likely to build. To accomplish this, you can use the "System.Net.WebClient" class. The simplest use of this, using the "using" pattern, is shown below: using (var webClient = n...

Angular has some magic under its hood. it enables binding DOM to real js variables. Angular uses a loop, named the "digest loop", which is called after any change of a variable - calling callbacks which update the DOM. For example, the ng-model directive attaches a keyup eventListener to...

angular.module('app', []) .controller('myController', ['$scope', function($scope){ $scope.person = { name: 'John Doe' }; }]); <div ng-app="app" ng-conroller="myController"> <input ng-model="person.name" /> <div ng-repeat="number i...

Be careful, this approach might be considered as a bad design for angular apps, since it requires programmers to remember both where functions are placed in the scope tree, and to be aware of scope inheritance. In many cases it would be preferred to inject a service (Angular practice - using scope ...