Tutorial by Examples: l

Processing tabular data with awk is very easy, provided that the input is correctly formatted. Most software producing tabular data use specific features of this family of formats, and awk programs processing tabular data are often specific to a data produced by a specific software. If a more gener...

Given a file using ; as a column delimiter. Permuting the first and the second column is accomplished by awk -F';' -v 'OFS=;' '{ swap = $2; $2 = $1; $1 = swap; print }'

Given a file using ; as a column delimiter. We compute the mean of the values in the second column with the following program, the provided input is the list of grades of a student group: awk -F';' '{ sum += $2 } END { print(sum / NR) }' <<EOF Alice;2 Victor;1 Barbara;1 Casper;4 Deborah;...

We assume a file using ; as a column delimiter. Selecting a specific set of columns only requires a print statement. For instance, the following program selects the columns 3, 4 and 7 from its input: awk -F';' -v 'OFS=;' '{ print $3, $4, $7 }' It is as usual possible to more carefully choose lin...

Given a file using ; as a column delimiter. We compute the median of the values in the second column with the following program, written for GNU awk. The provided input is the list of grades of a student group: gawk -F';' '{ sample[NR] = $2 } END { asort(sample); if(NR % 2 == 1) { p...

Use import to specify how a namespace from one library is used in the scope of another library. import 'dart:html'; The only required argument to import is a URI specifying the library. For built-in libraries, the URI has the special dart: scheme. For other libraries, you can use a file system p...

Unlike Java, Dart doesn’t have the keywords public, protected, and private. If an identifier starts with an underscore _, it’s private to its library. If you for example have class A in a separate library file (eg, other.dart), such as: library other; class A { int _private = 0; testA()...

If you import two libraries that have conflicting identifiers, then you can specify a prefix for one or both libraries. For example, if library1 and library2 both have an Element class, then you might have code like this: import 'package:lib1/lib1.dart'; import 'package:lib2/lib2.dart' as lib2; /...

If you want to use only part of a library, you can selectively import the library. For example: // Import only foo and bar. import 'package:lib1/lib1.dart' show foo, bar; // Import all names EXCEPT foo. import 'package:lib2/lib2.dart' hide foo;

Deferred loading (also called lazy loading) allows an application to load a library on demand, if and when it’s needed. To lazily load a library, you must first import it using deferred as. import 'package:deferred/hello.dart' deferred as hello; When you need the library, invoke loadLibrary() us...

For example we have WordCountService with countWords method: class WordCountService { def countWords(url: String): Map[String, Int] = { val sparkConf = new SparkConf().setMaster("spark://somehost:7077").setAppName("WordCount")) val sc = new SparkContext(sp...

Use pub build when you’re ready to deploy your web app. When you run pub build, it generates the assets for the current package and all of its dependencies, putting them into new directory named build. To use pub build, just run it in your package’s root directory. For example: $ cd ~/dart/hellowo...

iex(1)> name = "John" "John" iex(2)> greeting = "Hello, #{name}" "Hello, John" iex(3)> num = 15 15 iex(4)> results = "#{num} item(s) found." "15 item(s) found."

C99 Using the system header file stdbool.h allows you to use bool as a Boolean data type. true evaluates to 1 and false evaluates to 0. #include <stdio.h> #include <stdbool.h> int main(void) { bool x = true; /* equivalent to bool x = 1; */ bool y = false; /* equivalent t...

It is a good practice to provide expression string arguments as braced strings. The heading "Double Substitution" outlines important reasons behind the same. The expr command evaluates an operator-based expression string to calculate a value. This string is constructed from the arguments ...

To implement the equals method of an object easily you could use the EqualsBuilder class. Selecting the fields: @Override public boolean equals(Object obj) { if(!(obj instanceof MyClass)) { return false; } MyClass theOther = (MyClass) obj; EqualsBuilder builde...

To implement the hashCode method of an object easily you could use the HashCodeBuilder class. Selecting the fields: @Override public int hashCode() { HashCodeBuilder builder = new HashCodeBuilder(); builder.append(field1); builder.append(field2); builder.append(field3); ...

To implement the toString method of an object easily you could use the ToStringBuilder class. Selecting the fields: @Override public String toString() { ToStringBuilder builder = new ToStringBuilder(this); builder.append(field1); builder.append(field2); builder.append(field3...

When the view controller is presented within a tab bar controller, you can access the tab bar controller like this: Swift let tabBarController = viewController.tabBarController Objective-C UITabBarController *tabBarController = self.tabBarController; When the view controller is part on an n...

The var_dump function allows you to dump the contents of a variable (type and value) for debugging. Example: $array = [3.7, "string", 10, ["hello" => "world"], false, new DateTime()]; var_dump($array); Output: array(6) { [0]=> float(3.7) [1]=> ...