Tutorial by Examples: re

You must to add to web.xml a configuration tag like this: <context-param> <param-name>facelets.SKIP_COMMENTS</param-name> <param-value>true</param-value> </context-param> Now you can use normal HTML comments tag <!-- and --> <!-- <...

First lets create a vector called Vector1: set.seed(123) Vector1 <- rnorm(20) And add missing data to it: set.seed(123) Vector1[sample(1:length(Vector1), 5)] <- NA Now we can use the is.na function to subset the Vector Vector1 <- Vector1[!is.na(Vector1)] Now the resulting vect...

There might be times where you have a data frame and you want to remove all the rows that might contain an NA value, for that the function complete.cases is the best option. We will use the first 6 rows of the airquality dataset to make an example since it already has NAs x <- head(airquality) ...

A constant expression is an expression that yields a primitive type or a String, and whose value can be evaluated at compile time to a literal. The expression must evaluate without throwing an exception, and it must be composed of only the following: Primitive and String literals. Type ca...

ll | grep ^- | awk -F"." '{print $2 "." $3}' | awk -F":" '{print $2}' | awk '{$1=""; print $0}' | cut -c2- | awk -F"." '{print "mkdir ""$1"";mv ""$1"."$2"" ""$1"""}' >...

Java expressions are evaluated following the following rules: Operands are evaluated from left to right. The operands of an operator are evaluated before the operator. Operators are evaluated according to operator precedence Argument lists are evaluated from left to right. Simple Example I...

BFG Repo cleaner is an alternative to git filter-branch. It can be used to remove sensitive data or large files that were committed wrongly like binaries compiled from the source. It is written in Scala. Project website: BFG Repo Cleaner Requirements The Java Runtime Environment (Java 7 or above ...

Resource loading in Java comprises the following steps: Finding the Class or ClassLoader that will find the resource. Finding the resource. Obtaining the byte stream for the resource. Reading and processing the byte stream. Closing the byte stream. The last three steps are typically accomp...

React components that are pure functions of their props and do not require any internal state can be written as JavaScript functions instead of using the standard class syntax, as: import React from 'react' const HelloWorld = (props) => ( <h1>Hello, {props.name}!</h1> ); ...

SELECT 1 a, '' b from DUAL; AB1(null)

SELECT 3 * NULL + 5, 'Hello ' || NULL || 'world' from DUAL; 3*NULL+5'HELLO'||NULL||'WORLD'(null)Hello world

SELECT a column_with_null, NVL(a, 'N/A') column_without_null FROM (SELECT NULL a FROM DUAL); COLUMN_WITH_NULLCOLUMN_WITHOUT_NULL(null)N/A NVL is useful to compare two values which can contain NULLs : SELECT CASE WHEN a = b THEN 1 WHEN a <> b THEN 0 else -1 END comparison_without_n...

If the first parameter is NOT NULL, NVL2 will return the second parameter. Otherwise it will return the third one. SELECT NVL2(null, 'Foo', 'Bar'), NVL2(5, 'Foo', 'Bar') FROM DUAL; NVL2(NULL,'FOO','BAR')NVL2(5,'FOO','BAR')BarFoo

SELECT COALESCE(a, b, c, d, 5) FROM (SELECT NULL A, NULL b, NULL c, 4 d FROM DUAL); COALESCE(A,B,C,D,5)4 In some case, using COALESCE with two parameters can be faster than using NVL when the second parameter is not a constant. NVL will always evaluate both parameters. COALESCE will stop a...

A Frame is created like any other controls: <Frame x:Name="contentRoot" Navigated="OnNavigated" Navigating="OnNavigating" /> The navigated/navigating events can then be intercepted to cancel the navigation or show/hide the back button. private...

import cv2 def canny_webcam(): "Live capture frames from webcam and show the canny edge image of the captured frames." cap = cv2.VideoCapture(0) while True: ret, frame = cap.read() # ret gets a boolean value. True if reading is successful (I think). frame ...

An input port can be created in many ways, but usually the method starts with open-input-. String port You can use a string as a port using open-input-string. It will create a port that will be able to read from the string. (define p (open-input-string "(a . (b . (c . ()))) 34")) ...

Reading from an input port can be done in many ways. We can use the read method used by the REPL. It will read and interpret space separated expressions. Taking the example from the string port above. We can read from the port like this: (define p (open-input-string "(a . (b . (c . ()))) 3...

A pair can be create with the cons function. The name of the function stand for constructor. In Scheme, everything is pretty much based on pairs. (cons a b) The function return a pair containing the element a and b. The first parameter of cons is called car (Content Address Register) and the sec...

List in scheme are nothing else than a series of pairs nested in each other in the cdr of a cons. And the last cdr of a proper list is the empty list '(). To create the list (1 2 3 4), we'd have something like this: (cons 4 '()) > (4) (cons 3 (cons 4 '())) > (3 4) (cons 2 (cons 3 (cons 4...