Tutorial by Topics: co

The official vignette, "Reference semantics", is the best introduction to this topic. A reminder: DT[where, select|update|do, by] syntax is used to work with columns of a data.table. The "where" part is the i argument The "select|update|do" part is the j argument...

A reminder: DT[where, select|update|do, by] syntax is used to work with columns of a data.table. The "where" part is the i argument The "select|update|do" part is the j argument These two arguments are usually passed by position instead of by name.

The special symbol .SD is available in j of DT[i,j,by], capturing the Subset of Data for each by group surviving the filter, i. .SDcols is a helper. Type ?`special-symbols` for the official docs. A reminder: DT[where, select|update|do, by] syntax is used to work with columns of a data.table. T...

The sqlite3 command-line shell implements an additional set of commands (which are not available in programs that use the SQLite library). Official documentation: Special commands to sqlite3

public static GameObject Find(string name); public static GameObject FindGameObjectWithTag(string tag); public static GameObject[] FindGameObjectsWithTag(string tag); public static Object FindObjectOfType(Type type); public static Object[] FindObjectsOfType(Type type); Which method to...

Entity Framework (EF) Core is a lightweight and extensible version of the popular Entity Framework data access technology. EF Core is an object-relational mapper (O/RM) that enables .NET developers to work with a database using .NET objects. It eliminates the need for most of the data-access code...

if expression ... end if expression ... else ... end if expression ... elseif expression ... end if expression ... elseif expression ... else ... end ParameterDescriptionexpressionan expression that has logical meaning

The ^M character stands for a carriage return in Vim (<c-m> or just <CR>). Vim displays this character when at least on line in the file uses LF line endings. In other words, when Vim consider a file to have fileformat=unix but some lines do have carriage returns (CR), the carriage r...

Spring has made it so that configuring an ApplicationContext is extremely flexible. There are numerous ways to apply each type of configuration, and they can all be mixed and matched together nicely. Java configuration is a form of explicit configuration. A @Configuration annotated class is use...

REST stands for Representational State Transfer (sometimes spelled "ReST"). It relies on a stateless, client-server, cacheable communications protocol and mostly HTTP protocol is used. It is primarily used to build Web services that are lightweight, maintainable, and scalable. A service ba...

Hadoop v1 commands: hadoop fs -<command> Hadoop v2 commands: hdfs dfs -<command>

Parallel collections facilitate parallel programming by hiding low-level parallelization details. This makes taking advantage of multi-core architectures easy. Examples of parallel collections include ParArray, ParVector, mutable.ParHashMap, immutable.ParHashMap, and ParRange. A full list can be f...

constexpr is a keyword that can be used to mark a variable's value as a constant expression, a function as potentially usable in constant expressions, or (since C++17) an if statement as having only one of its branches selected to be compiled. The constexpr keyword was added in C++11 but for a...

The Flash concept is taken from Ruby on Rails and provides a way to pass temporary objects between the user views generated by the faces lifecycle. As in Rails, anything one places in the flash will be exposed to the next view encountered by the same user session and then cleared out. It is import...

This method is used to check weather WI-Fi is connected or not. isNetworkAvailable() : To check if Internet available on device ParameterDetailContextA reference of Activity context If internet connected then method will return true or false.