Tutorial by Examples: d

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...

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()...

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...

Fortran originally was designed for a fixed format form based on an 80 column punched card: Yes: This is a line of the author's own code These were created on a card punch machine, much like this: Images are original photography by the author The format, as shown on the illustrated sample ca...

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...

C of all versions, will effectively treat any integer value other than 0 as true for comparison operators and the integer value 0 as false. If you don't have _Bool or bool as of C99 available, you could simulate a Boolean data type in C using #define macros, and you might still find such things in...

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...

Parameters The first 4 parameters are passed in (in order) RCX, RDX, R8 and R9. XMM0 to XMM3 are used to pass floating point parameters. Any further parameters are passed on the stack. Parameters larger than 64bit are passed by address. Spill Space Even if the function uses less than 4 paramet...

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]=> ...

If you want PHP to display runtime errors on the page, you have to enable display_errors, either in the php.ini or using the ini_set function. You can choose which errors to display, with the error_reporting (or in the ini) function, which accepts E_* constants, combined using bitwise operators. P...

You can use gradle to have BuildConfig constants and res values on a per flavor basis. Just add the value to the flavor you want to support. android { defaultConfig { resValue "string", "app_name", "Full App" buildConfigField "boolean",...

Matlab supports synchronous and asynchronous communication with a serial port. It is important to chose the right communication mode. The choice will depend on: how the instrument you are communicating with behave. what other functions your main program (or GUI) will have to do aside from managi...

#include <stdio.h> int main(void) { /* define a small bit-field that can hold values from 0 .. 7 */ struct { unsigned int uint3: 3; } small; /* extract the right 3 bits from a value */ unsigned int value = 255 - 2; /* Binary 11111101 */ small.u...

You can convert a numeric string to various Java numeric types as follows: String to int: String number = "12"; int num = Integer.parseInt(number); String to float: String number = "12.0"; float num = Float.parseFloat(number); String to double: String double = "1...