# Tutorial by Examples: boolean

## The boolean primitive

A boolean can store one of two values, either true or false boolean foo = true; System.out.println(&quot;foo = &quot; + foo); // foo = true boolean bar = false; System.out.println(&quot;bar = &quot; + bar); // bar = false boolean notFoo = !foo; System.out.prin...

## Logic Operators with Booleans

var x = true, y = false; AND This operator will return true if both of the expressions evaluate to true. This boolean operator will employ short-circuiting and will not evaluate y if x evaluates to false. x &amp;&amp; y; This will return false, because y is false. OR This operator wil...

## Logic Operators with Non-boolean values (boolean coercion)

Logical OR (||), reading left to right, will evaluate to the first truthy value. If no truthy value is found, the last value is returned. var a = 'hello' || ''; // a = 'hello' var b = '' || []; // b = [] var c = '' || undefined; // c = undefined var d = 1 |...

## Searched CASE in SELECT (Matches a boolean expression)

The searched CASE returns results when a boolean expression is TRUE. (This differs from the simple case, which can only check for equivalency with an input.) SELECT Id, ItemId, Price, CASE WHEN Price &lt; 10 THEN 'CHEAP' WHEN Price &lt; 20 THEN 'AFFORDABLE' ELSE 'EXPENSIVE' E...

## Short-circuiting in boolean operators

The and-operator (&amp;&amp;) and the or-operator (||) employ short-circuiting to prevent unnecessary work if the outcome of the operation does not change with the extra work. In x &amp;&amp; y, y will not be evaluated if x evaluates to false, because the whole expression is guaranteed to be false....

## Boolean

Boolean is a type, having two values, denoted as true or false. This code sets the value of \$foo as true and \$bar as false: \$foo = true; \$bar = false; true and false are not case sensitive, so TRUE and FALSE can be used as well, even FaLsE is possible. Using lower case is most common and recom...

## Using Boolean in if statement

Due to auto unboxing, one can use a Boolean in an if statement: Boolean a = Boolean.TRUE; if (a) { // a gets converted to boolean System.out.println(&quot;It works!&quot;); } That works for while, do while and the condition in the for statements as well. Note that, if the Boolean is null...

## Boolean Logical Operators

The OR (||) operator returns true if one of its two operands evaluates to true, otherwise it returns false. For example, the following code evaluates to true because at least one of the expressions either side of the OR operator is true: if (10 &lt; 20) || (20 &lt; 10) { print(&quot;Expression...

## Converting a number to a boolean

Boolean(0) === false Boolean(0) will convert the number 0 into a boolean false. A shorter, but less clear, form: !!0 === false

## Converting a string to a boolean

To convert a string to boolean use Boolean(myString) or the shorter but less clear form !!myString All strings except the empty string (of length zero) are evaluated to true as booleans. Boolean('') === false // is true Boolean(&quot;&quot;) === false // is true Boolean('0') === fals...

## Converting to boolean

Boolean(...) will convert any data type into either true or false. Boolean(&quot;true&quot;) === true Boolean(&quot;false&quot;) === true Boolean(-1) === true Boolean(1) === true Boolean(0) === false Boolean(&quot;&quot;) === false Boolean(&quot;1&quot;) === true Boolean(&quot;0&quot;) === t...

## `and` and `or` are not guaranteed to return a boolean

When you use or, it will either return the first value in the expression if it's true, else it will blindly return the second value. I.e. or is equivalent to: def or_(a, b): if a: return a else: return b For and, it will return its first value if it's false, else it r...

## Boolean parameter

Define: module.config(['\$urlMatcherFactoryProvider', function(\$urlMatcherFactory) { \$urlMatcherFactory.type('boolean', { decode: function(val) { return val == true || val == &quot;true&quot; }, encode: function(val) { return val ? 1 : 0; }, equals: function(a, b) { return this.is(...

## Boolean indexing

arr = np.arange(7) print(arr) # Out: array([0, 1, 2, 3, 4, 5, 6]) Comparison with a scalar returns a boolean array: arr &gt; 4 # Out: array([False, False, False, False, False, True, True], dtype=bool) This array can be used in indexing to select only the numbers greater than 4: arr[arr&...

## Boolean indexing

One can select rows and columns of a dataframe using boolean arrays. import pandas as pd import numpy as np np.random.seed(5) df = pd.DataFrame(np.random.randint(100, size=(5, 5)), columns = list(&quot;ABCDE&quot;), index = [&quot;R&quot; + str(i) for i in range(5)]) print (...

## Boolean Logic Expressions

Boolean logic expressions, in addition to evaluating to True or False, return the value that was interpreted as True or False. It is Pythonic way to represent logic that might otherwise require an if-else test. And operator The and operator evaluates all expressions and returns the last expressi...

## Convert a boolean to visibility value

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: &lt;Window x:Class=&quot;StackOverflo...

## Boolean search

+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...

## Boolean operators

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...

## Validating Boolean Values

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...

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