Tutorial by Examples: r

Converting the rest of a sequence to a map

Destructuring also gives you the ability to interpret a sequence as a map: (def my-vec [:a 1 :b 2]) (def my-lst '("smthg else" :c 3 :d 4)) (let [[& {:keys [a b]}] my-vec [s & {:keys [c d]} my-lst] (+ a b c d)) ;= 10 It is useful for defining functions with named p...

clojure • Clojure destructuring

Predicates with side effects

Predicates that produce side effects leave the realm of pure logic. These are for example: writeq/1 read/1 format/2 Side effects are phenomena that cannot be reasoned about within the program. For example, deletion of a file or output on the system terminal.

Prolog Language • Extra-logical Predicates

Meta-logical predicates

Predicates that reason about instantiations are called meta-logical. Examples are: var/1 ground/1 integer/1 These predicates are outside the realm of pure monotonic logic programs, because they break properties like commutativity of conjunction. Other predicates that are meta-logical includ...

Prolog Language • Extra-logical Predicates

All-solutions predicates

Predicates that reason about all solutions are extra-logical. These are for example: setof/3 findall/3 bagof/3

Prolog Language • Extra-logical Predicates

CLP(FD) constraints

CLP(FD) constraints are completely pure relations. They can be used in all directions for declarative integer arithmetic: ?- X #= 1+2. X = 3. ?- 3 #= Y+2. Y = 1.

Prolog Language • Logical Purity

Date Arithmetic - Difference between Dates in Days, Hours, Minutes and/or Seconds

In oracle, the difference (in days and/or fractions thereof) between two DATEs can be found using subtraction: SELECT DATE '2016-03-23' - DATE '2015-12-25' AS difference FROM DUAL; Outputs the number of days between the two dates: DIFFERENCE ---------- 89 And: SELECT TO_DATE( '201...

Oracle Database • Dates

Looping through an array

Our example array: arr=(a b c d e f) Using a for..in loop: for i in "${arr[@]}"; do echo "$i" done 2.04 Using C-style for loop: for ((i=0;i<${#arr[@]};i++)); do echo "${arr[$i]}" done Using while loop: i=0 while [ $i -lt ${#arr[@]} ]; do...

Bash • Arrays

Hello World

<!DOCTYPE html> <html> <head> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta http-equiv="Content-Type" content="text/html;charset=UTF-8"/> <title>SAPUI5 Hello World</title> <!-- ...

sapui5 • Getting started with sapui5

Throwing exception in a lock statement

Following code will release the lock. There will be no problem. Behind the scenes lock statement works as try finally lock(locker) { throw new Exception(); } More can be seen in the C# 5.0 Specification: A lock statement of the form lock (x) ... where x is an expression of a referenc...

C# Language • Lock Statement

Partial Application

Partial application means calling a function with less arguments than it has and saving the result as another function (that waits for the rest of the arguments). multiplyBy: Int -> Int -> Int multiplyBy x y = x * y multiplyByTwo : Int -> Int -- one Int has disappeared! we ...

Elm Language • Functions and Partial Application

Converting string to upper case

The function toupper will convert a string to upper case (capital letters). For example: BEGIN { greeting = "hello" loud_greeting = toupper(greeting) print loud_greeting } This code will output "HELLO" when run.

awk • String manipulation functions

Simple "Hello World" Project

Given a C++ source file main.cpp defining a main() function, an accompanying CMakeLists.txt file (with the following content) will instruct CMake to generate the appropriate build instructions for the current system and default C++ compiler. main.cpp (C++ Hello World Example) #include <iostream...

cmake • Getting started with cmake

Creating Processes

We create a new concurrent process by calling the spawn function. The spawn function will get as parameter a function Fun that the process will evaluate. The return value of the spawn function is the created process identifier (pid). 1> Fun = fun() -> 2+2 end. #Fun<erl_eval.20.52032458&gt...

Erlang Language • Processes

Functions and Properties in enums

Enum classes can also declare members (i.e. properties and functions). A semicolon (;) must be placed between the last enum object and the first member declaration. If a member is abstract, the enum objects must implement it. enum class Color { RED { override val rgb: Int = 0xFF0000 ...

Kotlin • Enum

Routing using YAML

The routing configuration is included in your app/config/config.yml file, by default the app/config/routing.yml file. From there you can link to your own routing configuration in a bundle # app/config/routing.yml app: resource: "@AppBundle/Resources/config/routing.yml" It migh...

symfony3 • Routing

Routing using annotations

The routing configuration is included in your app/config/config.yml file, by default the app/config/routing.yml file. From there you can link to the controllers that have annotated routing configuration: # app/config/routing.yml app: resource: "@AppBundle/Controller" type: ...

symfony3 • Routing

Hello World

File: test.cfm Tag Implementation <cfoutput>Hello World!</cfoutput> CFScript Implementation <cfscript> writeOutput("Hello World!"); </cfscript>

coldfusion • Getting started with coldfusion

Printing to a browser's debugging console

A browser's debugging console can be used in order to print simple messages. This debugging or web console can be directly opened in the browser (F12 key in most browsers – see Remarks below for further information) and the log method of the console Javascript object can be invoked by typing the fol...

JavaScript • Console

Hello World

Begin by including highcharts.js in your index.html <html> <head> <script src="http://code.highcharts.com/highcharts.js"></script> </head> Add a <div> to contain your chart <body> <div id="chart"> <!...

highcharts • Getting started with highcharts

Saving a read-only file edited in Vim

Sometimes, we may open a file which we do not have permission to write in Vim without using sudo. Use this command to save a read-only file edited in Vim. :w !sudo tee > /dev/null % Which you could map to :w!! in your .vimrc: cmap w!! w !sudo tee > /dev/null % You will be presented a ...

vim • Getting started with vim