Tutorial by Examples: conditional

6.0 Introduced in C# 6.0, the Null Conditional Operator ?. will immediately return null if the expression on its left-hand side evaluates to null, instead of throwing a NullReferenceException. If its left-hand side evaluates to a non-null value, it is treated just like a normal . operator. Note tha...

Adding a Conditional attribute from System.Diagnostics namespace to a method is a clean way to control which methods are called in your builds and which are not. #define EXAMPLE_A using System.Diagnostics; class Program { static void Main() { ExampleA(); // This method will ...

if v:version >= 704 " Do something if Vim is the right version. endif if has('patch666') " Do something if Vim has the right patch-level. endif if has('feature') " Do something if Vim is built with 'feature'. endif See :help has-patch and :help feature-li...

The @if control directive evaluates a given expression and if it returns anything other than false, it processes its block of styles. Sass Example $test-variable: true !default =test-mixin @if $test-variable display: block @else display: none .test-selector +test-mixin ...

Conditional contexts in Lua (if, elseif, while, until) do not require a boolean. Like many languages, any Lua value can appear in a condition. The rules for evaluation are simple: false and nil count as false. Everything else counts as true. if 1 then print("Numbers work.") ...

Conditional expressions can be done with ~[ and ~]. The clauses of the expression are separated using ~;. By default, ~[ takes an integer from the argument list, and picks the corresponding clause. The clauses start at zero. (format t "~@{~[First clause~;Second clause~;Third clause~;Fourth cl...

Ruby has an or-equals operator that allows a value to be assigned to a variable if and only if that variable evaluates to either nil or false. ||= # this is the operator that achieves this. this operator with the double pipes representing or and the equals sign representing assigning of a valu...

In Common Lisp, if is the simplest conditional construct. It has the form (if test then [else]) and is evaluated to then if test is true and else otherwise. The else part can be omitted. (if (> 3 2) "Three is bigger!" "Two is bigger!") ;;=> "Three is bigger...

LOOP has its own IF statement that can control how the clauses are executed: (loop repeat 1000 for x = (random 100) if (evenp x) collect x into evens else collect x into odds finally (return (values evens odds))) Combining multiple clauses in an IF ...

Send a 304 Not Modified response status from the server send in response to a client request that contains headers If-Modified-Since and If-None-Match, if the request resource hasn’t changed. For example if a client request for a web page includes the header If-Modified-Since: Fri, 22 Jul 2016 14:3...

When using show.bind the element remains in the page and is either hidden or visible through the use of display:none or display:block behind the scenes. export class MyViewModel { isVisible = false; } <template> <div show.bind="isVisible"><strong>I can be b...

Unlike show.bind when using if.bind the element will be removed from the page if the supplied binding value is false or added into the page if the value is true. export class MyViewModel { isVisible = false; } <template> <div if.bind="isVisible"><strong>If ...

Use Conditionals via (syntax is in [brackets]): when [when:] Task: - name: run if operating system is debian command: echo "I am a Debian Computer" when: ansible_os_family == "Debian" loops [with_items:] loops [with_dicts:] Custom Facts [ wh...

Java provides a conditional-and and a conditional-or operator, that both take one or two operands of type boolean and produce a boolean result. These are: && - the conditional-AND operator, || - the conditional-OR operators. The evaluation of <left-expr> && <righ...

You use the condition attribute to specify the condition to use. <cfset myVar=false> <cfloop condition="myVar eq false"> <cfoutput> myVar = <b>#myVar#</b> (still in loop)<br /> </cfoutput> <cfif RandRange(1,10) eq 10> ...

Extension Method can work on null references, but you can use ?. to null-check anyway. public class Person { public string Name {get; set;} } public static class PersonExtensions { public static int GetNameLength(this Person person) { return person == null ? -1 : pers...

Sometimes you may need to validate record only under certain conditions. class User < ApplicationRecord validates :name, presence: true, if: :admin? def admin? conditional here that returns boolean value end end If you conditional is really small, you can use a Proc: class ...

pushunique!(A, x) = x in A ? A : push!(A, x) The ternary conditional operator is a less wordy if...else expression. The syntax specifically is: [condition] ? [execute if true] : [execute if false] In this example, we add x to the collection A only if x is not already in A. Otherwise, we jus...

The markdown help states Available conditionals are gt, gte, lt, lte, eq, and neq. <!-- if version [eq C++03] --> eq equal to <!-- end version if --> <!-- if version [neq C++03] --> neq not equal to <!-- end version if --> <!-- if version [gt C++03] -...

Multiple conditions can be used. <!-- if version [lte 1.2.0] [gt 1.3.12] [gt 1.4.9] [neq 1.2.0] [eq 1.5.7] --> content <!-- end version if -->