Tutorial by Examples: an

How do foldFree and iterM work?

There are some functions to help tear down Free computations by interpreting them into another monad m: iterM :: (Functor f, Monad m) => (f (m a) -> m a) -> (Free f a -> m a) and foldFree :: Monad m => (forall x. f x -> m x) -> (Free f a -> m a). What are they doing? First l...

Haskell Language • Free Monads

IComparable as an Example of Implementing an Interface

Interfaces can seem abstract until you seem them in practice. The IComparable and IComparable<T> are great examples of why interfaces can be helpful to us. Let's say that in a program for a online store, we have a variety of items you can buy. Each item has a name, an ID number, and a price. ...

C# Language • Interfaces

Including LaTeX Preample Commands

There are two possible ways of including LaTeX preamble commands (e.g. \usepackage) in a RMarkdown document. 1. Using the YAML option header-includes: --- title: "Including LaTeX Preample Commands in RMarkdown" header-includes: - \renewcommand{\familydefault}{cmss} - \usepacka...

R Language • Creating reports with RMarkdown

Parsing JavaScript Generated Page with Jsoup and HtmUnit

page.html - source code <html> <head> <script src="loadData.js"></script> </head> <body onLoad="loadData()"> <div class="container"> <table id="data" border="1"> <...

Jsoup • Parsing Javascript Generated Pages

Using the default Form instance

VB.NET offers default Form instances. The developer does not need to create the instance as it is created behind the scenes. However, it is not preferable to use the default instance all but the simplest programs. Public Class Form1 Public Sub Foo() MessageBox.Show("Bar") ...

Visual Basic .NET Language • Working with Windows Forms

Installing nginx and setting it up for uWSGI

Now we want to install nginx to serve our application. sudo apt-get install nginx # on debian/ubuntu Then we create a configuration for our website cd /etc/nginx/site-available # go to the configuration for available sites # create a file flaskconfig with your favourite editor flaskconfig...

Flask • Deploying Flask application using uWSGI web server with Nginx

Reads file (/etc/passwd) line by line and field by field

#!/bin/bash FILENAME="/etc/passwd" while IFS=: read -r username password userid groupid comment homedir cmdshell do echo "$username, $userid, $comment $homedir" done < $FILENAME In unix password file, user information is stored line by line, each line consisting of i...

Bash • Read a file (data stream, variable) line-by-line (and/or field-by-field)?

How to compose values and functions using common operators

In Object Oriented Programming a common task is to compose objects (values). In Functional Programming it is as common task to compose values as well as functions. We are used to compose values from our experience of other programming languages using operators like +, -, *, / and so on. Value co...

F# • Operators

Using Pools and Workers

Pooling provides a higher level abstraction of the Worker functionality, including the management of references in the way required by pthreads. From: http://php.net/manual/en/class.pool.php Pools and workers provide an higher level of control and ease of creating multi-threaded <?php // T...

PHP • Multi Threading Extension

Getting and setting system volume

Audio stream types There are different profiles of ringtone streams. Each one of them has it's different volume. Every example here is written for AudioManager.STREAM_RING stream type. However this is not the only one. The available stream types are: STREAM_ALARM STREAM_DTMF STREAM_MUSIC STR...

Android • MediaPlayer

Entity with sequence managed Id

Here we have a class and we want the identity field (userUid) to have its value generated via a SEQUENCE in the database. This SEQUENCE is assumed to be called USER_UID_SEQ, and can be created by a DBA, or can be created by the JPA provider. @Entity @Table(name="USER") public class User...

jpa • Basic mapping

Adapters and Consumers

Iterator methods can be broken into two distinct groups: Adapters Adapters take an iterator and return another iterator // Iterator Adapter // | | let my_map = (1..6).map(|x| x * x); println!("{:?}", my_map); Output Map { iter: 1..6 } Note that the v...

Rust • Iterators

Remove trace logging (and other) statements at build time

If you want to remove calls to certain methods, assuming they return void and have no side affects (as in, calling them doesn't change any system values, reference arguments, statics, etc.) then you can have ProGuard remove them from the output after the build is complete. For example, I find this ...

Android • ProGuard - Obfuscating and Shrinking your code

Using Deref and AsRef for function arguments

For functions that need to take a collection of objects, slices are usually a good choice: fn work_on_bytes(slice: &[u8]) {} Because Vec<T> and arrays [T; N] implement Deref<Target=[T]>, they can be easily coerced to a slice: let vec = Vec::new(); work_on_bytes(&vec); le...

Rust • Auto-dereferencing

Handling Specific Types Unknown at Compile Time

The following output equivalent results: class IfElseExample { public string DebugToString(object a) { if (a is StringBuilder) { return DebugToStringInternal(a as StringBuilder); } else if (a is List<string>) { ...

C# Language • Dynamic type

Creating and Displaying an ALV

This example portrays the most simple ALV creation using the cl_salv_table class and no additional formatting options. Additional formatting options would be included after the TRY ENDTRY block and before the alv->display( ) method call. All subsequent examples using the ABAP Objects approach to...

ABAP • ABAP GRID List Viewer (ALV)

Hide Columns in an ALV

This example hides the MANDT (client) field from the ALV. Note that the parameter passed to get_column( ) must be capitalized in order for this to work. alv->get_columns( )->get_column( 'MANDT' )->set_visible( if_salv_c_bool_sap=>false ).

ABAP • ABAP GRID List Viewer (ALV)

Rename Column Headings in an ALV

The column text may change upon the horizontal resizing of a column. There are three methods to accomplish this: Method NameMaximum Length of Headingset_short_text10set_medium_text20set_long_text40 The following example shows usage of all three. A column object is declared and instantiated as a re...

ABAP • ABAP GRID List Viewer (ALV)

Programmatically manage UIView insertion and deletion into and from another UIView

Suppose you have a parentView into which you want to insert a new subView programmatically (eg. when you want to insert an UIImageView into a UIViewController's view), than you can do it as below. Objective-C [parentView addSubview:subView]; Swift parentView.addSubview(subView) You can also...

iOS • UIView

Ignoring build variant

For some reasons you may want to ignore your build variants. For example: you have 'mock' product flavour and you use it only for debug purposes, such as unit/instrumentation tests. Let's ignore mockRelease variant from our project. Open build.gradle file and write: // Remove mockRelease as it...

Android • Gradle for Android