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016. undefined test

JavaScript

v === undefined

Lua

v == nil

Io

not_defined := false
e := try(v)
e catch(Exception,
  not_defined = true
)

VBScript

Perl

PHP

Python

Ruby

PowerShell

Scala

F#

C

C++

C++Builder

VC++

C#

Java

Objective-C

D

VB

VB.NET

Delphi

Ada

PL/SQL

T-SQL