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The null coalescing operator is a binary operator that is part of the syntax for a basic conditional expression in several programming languages, such as (in alphabetical order): C# [1] since version 2.0, [2] Dart [3] since version 1.12.0, [4] PHP since version 7.0.0, [5] Perl since version 5.10 as logical defined-or, [6] PowerShell since 7.0.0, [7] and Swift [8] as nil-coalescing operator.
In JavaScript, the empty string (""), null, undefined, NaN, +0, −0 and false [3] are sometimes called falsy (of which the complement is truthy) to distinguish between strictly type-checked and coerced Booleans (see also: JavaScript syntax#Type conversion). [4] As opposed to Python, empty containers (Arrays, Maps, Sets) are considered truthy.
In C, the number 0 or 0.0 is false, and all other values are treated as true. In JavaScript , the empty string ( "" ), null , undefined , NaN , +0, −0 and false [ 28 ] are sometimes called falsy (of which the complement is truthy ) to distinguish between strictly type-checked and coerced Booleans (see also: JavaScript syntax#Type conversion ...
These include numerical equality (e.g., 5 = 5) and inequalities (e.g., 4 ≥ 3). In programming languages that include a distinct boolean data type in their type system, like Pascal, Ada, Python or Java, these operators usually evaluate to true or false, depending on if the conditional relationship between the two operands holds or not.
A string is considered true if it contains at least one non-whitespace character (thus, for example, the #if function interprets the strings "0" and "FALSE" as true values, not false). Any string containing only whitespace or no characters at all will be treated as false (thus #if interprets " " and "", as well as undefined parameters, as false ...
var x1 = 0; // A global variable, because it is not in any function let x2 = 0; // Also global, this time because it is not in any block function f {var z = 'foxes', r = 'birds'; // 2 local variables m = 'fish'; // global, because it wasn't declared anywhere before function child {var r = 'monkeys'; // This variable is local and does not affect the "birds" r of the parent function. z ...
where p = 0.3275911, a 1 = 0.254829592, a 2 = −0.284496736, a 3 = 1.421413741, a 4 = −1.453152027, a 5 = 1.061405429 All of these approximations are valid for x ≥ 0 . To use these approximations for negative x , use the fact that erf x is an odd function, so erf x = −erf(− x ) .
The false positive rate (FPR) is the proportion of all negatives that still yield positive test outcomes, i.e., the conditional probability of a positive test result given an event that was not present. The false positive rate is equal to the significance level. The specificity of the test is equal to 1 minus the false positive rate.