Tutorial by Examples: bool

This example hides the red box (border) if the checkbox is not checked by making use of an IValueConverter. Note: The BooleanToVisibilityConverter used in the example below is a built-in value converter, located in the System.Windows.Controls namespace. XAML: <Window x:Class="StackOverflo...

+firstname:john +surname:doe Matches documents where firstname is john and surname is doe. + predix indicates that the search term must occur (AND). +firstname:john -surname:doe Matches documents where firstname is john and surname is not doe. - predix indicates that the search term must not occu...

There are two kinds of boolean operators in Elixir: boolean operators (they expect either true or false as their first argument) x or y # true if x is true, otherwise y x and y # false if x is false, otherwise y not x # false if x is true, otherwise true All of booleans...

var_dump(filter_var(true, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // true var_dump(filter_var(false, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // false var_dump(filter_var(1, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE)); // true var_dump(filter_var(0, FILTER_VALIDATE_BOOL...

Keyword for storing the Boolean values true and false. bool is an alias of System.Boolean. The default value of a bool is false. bool b; // default value is false b = true; // true b = ((5 + 2) == 6); // false For a bool to allow null values it must be initialized as a bool?. The default val...

bool literals are either true or false; bool b = true;

A boolean represents the most basic datatype in TypeScript, with the purpose of assigning true/false values. // set with initial value (either true or false) let isTrue: boolean = true; // defaults to 'undefined', when not explicitely set let unsetBool: boolean; // can ...

We define the type of boolean expressions whose atoms are identified by strings as type expr = | Atom of string | Not of expr | And of expr * expr | Or of expr * expr and can evaluate these expressions using an oracle : string -> bool giving the values of the atoms we find as follows: le...

Booleans and other values When dealing with lua it is important to differentiate between the boolean values true and false and values that evaluate to true or false. There are only two values in lua that evaluate to false: nil and false, while everything else, including the numerical 0 evaluate to...

Actually any value different from NIL is considered a true value in Common Lisp. For instance: CL-USER> (let ((a (+ 2 2))) (if a a "Oh my! 2 + 2 is equal to NIL!")) 4 This fact can be combined with the boolean operators to make programs m...

With the ~ selector, you can easily implement a global accessible boolean without using JavaScript. Add boolean as a checkbox To the very beginning of your document, add as much booleans as you want with a unique id and the hidden attribute set: <input type="checkbox" id="sideba...

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...

C99 Added in the C standard version C99, _Bool is also a native C data type. It is capable of holding the values 0 (for false) and 1 (for true). #include <stdio.h> int main(void) { _Bool x = 1; _Bool y = 0; if(x) /* Equivalent to if (x == 1) */ { puts("T...

Dim Value As Boolean A Boolean is used to store values that can be represented as either True or False. Internally, the data type is stored as a 16 bit value with 0 representing False and any other value representing True. It should be noted that when a Boolean is cast to a numeric type, all of...

If you get an error like this: Fatal error: Call to a member function fetch_assoc() on boolean in C:\xampp\htdocs\stack\index.php on line 7 Other variations include something along the lines of: mysql_fetch_assoc() expects parameter 1 to be resource, boolean given... These errors mean that t...

Converter between boolean and visibility. Get bool value on input and returns Visibility value. NOTE: This converter have already exists in System.Windows.Controls namespace. public sealed class BooleanToVisibilityConverter : IValueConverter { /// <summary> /// Convert bool or Nu...

All integers or pointers can be used in an expression that is interpreted as "truth value". int main(int argc, char* argv[]) { if (argc % 4) { puts("arguments number is not divisible by 4"); } else { puts("argument number is divisible by 4"); } ... ...

Python 2.x2.7 In Python 2, if you want to define a class boolean value by yourself, you need to implement the __nonzero__ method on your class. The value is True by default. class MyClass: def __nonzero__(self): return False my_instance = MyClass() print bool(MyClass) # Tru...

Returns true or false, which indicates whether the regexp is matched or not without updating $~ and other related variables. If the second parameter is present, it specifies the position in the string to begin the search. /R.../.match?("Ruby") #=> true /R.../.match?("Ruby&quot...

Any value in Clojure is considered truthy unless it is false or nil. You can find the truthiness of a value with (boolean value). You can find the truthiness of a list of values using (or), which returns true if any arguments are truthy, or (and) which returns true if all arguments are truthy. =&gt...