In computing, a condition where an expression does not have a correct value
For other uses, see Undefined.
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In computing (particularly, in programming), undefined value is a condition where an expression does not have a correct value, although it is syntactically correct. An undefined value must not be confused with empty string, Boolean "false" or other "empty" (but defined) values. Depending on circumstances, evaluation to an undefined value may lead to exception or undefined behaviour, but in some programming languages undefined values can occur during a normal, predictable course of program execution.
Dynamically typed languages usually treat undefined values explicitly when possible. For instance, Perl has undef operator[1] which can "assign" such value to a variable. In other type systems an undefined value can mean an unknown, unpredictable value, or merely a program failure on attempt of its evaluation. Nullable types offer an intermediate approach; see below.
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programming), undefinedvalue is a condition where an expression does not have a correct value, although it is syntactically correct. An undefinedvalue must not...
correct valueUndefined variable Undefined, a function or variable lacking a declaration Undefined, a variable lacking initialization Undefined, an unavailable...
In computer programming, undefined behavior (UB) is the result of executing a program whose behavior is prescribed to be unpredictable, in the language...
returned when the return statement is omitted, while in JavaScript the valueundefined is returned. In Windows PowerShell all evaluated expressions which...
which represents absurdum under the Curry–Howard correspondence The "undefinedvalue" in quantum physics interpretations that reject counterfactual definiteness...
principal value, named after Augustin-Louis Cauchy, is a method for assigning values to certain improper integrals which would otherwise be undefined. In this...
X is undefined. Similarly, the Cauchy distribution, as discussed above, has undefined expectation. The following table gives the expected values of some...
evaluates to the undefined type in JS. I added the void operator to JS before Netscape 2 shipped to make it easy to discard any non-undefinedvalue in a javascript:...
\\{\text{undefined}}&{\text{if }}x=0{\text{ and }}y=0.\end{cases}}} Notes: This produces results in the range (−π, π]. As mentioned above, the principal value...
leave it unchanged, and some set it to an undefinedvalue. Shifts and multiplies do permit a well-defined value, but it is not consistently implemented...
.. undefined <altitude> MAY assume that the URI refers to the respective location on Earth's physical surface." However, "... an <altitude> value of 0...
automatic creation of new arrays and hashes as required every time an undefinedvalue is dereferenced. Perl autovivification allows a programmer to refer...
respond to undefined variables. Each code snippet is followed by an error message (if any). (setf y x) *** - EVAL: variable X has no value int main()...
means that values cannot be accessed before they are declared; forward reference is not possible. With var a variable's value is undefined until it is...
Julian; Nethercote, Nicholas (10 April 2005). "Using Valgrind to detect undefinedvalue errors with bit-precision". Proceedings of the USENIX Annual Technical...
any arbitrary type, including sets and tuples themselves, except the undefinedvalue om (sometimes capitalized: OM). Maps are provided as sets of pairs...
categorical predictors because the natural logarithm of zero is an undefinedvalue so that the final solution to the model cannot be reached. To remedy...
Value at risk (VaR) is a measure of the risk of loss of investment/Capital. It estimates how much a set of investments might lose (with a given probability)...
00, is a mathematical expression that is either defined as 1 or left undefined, depending on context. In algebra and combinatorics, one typically defines...
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