Tutorial by Examples: on

ALTER TABLE foo ENGINE=InnoDB; This converts the table, but does not take care of any differences between the engines. Most differences will not matter, especially for small tables. But for busier tables, other considerations should be considered. Conversion considerations

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <circle r="30" cx="100" cy="100" fill="rgb(255, 0, 0)" stroke="rgb(0, 255, 0)" /> <rect x="200" y="200" w...

PrimitiveBoxed TypeMemory Size of primitive / boxedbooleanBoolean1 byte / 16 bytesbyteByte1 byte / 16 bytesshortShort2 bytes / 16 bytescharChar2 bytes / 16 bytesintInteger4 bytes / 16 byteslongLong8 bytes / 16 bytesfloatFloat4 bytes / 16 bytesdoubleDouble8 bytes / 16 bytes Boxed objects always requ...

UPDATE person SET state = 'NY' WHERE city = 'New York';

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...

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 <-...

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 ...

The on.exit() function is handy for variable clean up if global variables must be assigned. Some parameters, especially those for graphics, can only be set globally. This small function is common when creating more specialized plots. new_plot <- function(...) { old_pars <- par(m...

Installing the haystack package pip install django-haystack Configuration Add haystack to your project's INSTALLED_APPS inside of your settings.py file: # settings.py INSTALLED_APPS = [ 'django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', # Put...

Create custom class for calling multipart/form-data HttpURLConnection request MultipartUtility.java public class MultipartUtility { private final String boundary; private static final String LINE_FEED = "\r\n"; private HttpURLConnection httpConn; priva...

The option -v followed by an assignment of the form variable=value can be used to pass parameters to an awk program. This is illustrated by the punishment program below, whose job is to write count times the sentence “I shall not talk in class.” on standard output. The following example uses the v...

ng-model-options allows to change the default behavior of ng-model, this directive allows to register events that will fire when the ng-model is updated and to attach a debounce effect. This directive accepts an expression that will evaluate to a definition object or a reference to a scope value. ...

// 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); } }

// Checks a string to see if it is a palindrome bool function IsPalindrome(string input) { if (input.size() <= 1) { return true; } else if (input[0] == input[input.size() - 1]) { return IsPalindrome(input.substr(1,input.size() - 2)); } else { r...

Custom events usually need custom event arguments containing information about the event. For example MouseEventArgs which is used by mouse events like MouseDown or MouseUp events, contains information about Location or Buttons which used to generate the event. When creating new events, to create a...

If you have a list, and you want to use the elements of that list as the arguments to a function, what you want is apply: > (apply string-append (list "hello" " " "and hi" " " "are both words")) "hello and hi are both words" > (app...

Functions in Racket can be created with the lambda form. The form takes a list of arguments and a body. (lambda (x y) (* x y)) In the example above, the function takes in two arguments and returns the result of multiplying them. > ((lambda (x y) (* x y)) 4 4) 16 > ((lambda (x y) (* x y)...

Instrument your code with console.trace() calls that print current JavaScript call stacks:

Place assertions in your JavaScript code by calling console.assert() with the error condition as the first parameter. When this expression evaluates to false, you will see a corresponding console record: