what is the difference between nil and null?
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In short they all are 0 and nothing else. The difference is that while NULL represents zero for any pointer, nil is specific to objects (e.g., id) and Nil is specific to class pointers.
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As you can see so far, null and undefined are different, but share some similarities. Thus, it makes sense that null does not strictly equal undefined . But, and this may surprise you, null loosely equals undefined . In JavaScript, a double equals tests for loose equality and preforms type coercion.
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In Objective-C there was no need to make a difference between them because you can call methods on nil in Objective-C. Also, there was no way in Objective-C to prevent users from assigning nil to a property. The resulting contract is that text can be optional. In Objective-C that makes no difference.
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If an element has the xsi:nil attribute specified, it indicates that the element is present but has no value, and therefore no content is associated with it. If an XML schema has defined the nillable attribute as true, then it is mapped as a required attribute that takes a boolean value.
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One way to check for null in JavaScript is to check if a value is loosely equal to null using the double equality == operator: ... So, when programming to check if a variable has any value at all before trying to process it, you can use == null to check for either null or undefined .
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There is one more major difference between the two methods is when the object we are converting is an array. When you convert an array using Object. ... Second difference is when the object is null, ValueOf() returns a String "null", while toString() will return null pointer exception.
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and zero is an integer constant. So basically NULL is 0 in pointer terms. In SQL databases this difference is very important. NULL in SQL basically means that the value is 'undefined' whereas 0 is a defined value.
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NULL means it does not have any value not even garbage value. ZERO is an integer value. BLANK is simply a empty String value.
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The is_null() function checks whether a variable is NULL or not. This function returns true (1) if the variable is NULL, otherwise it returns false/nothing.
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['JavaScript (and by extension TypeScript) has two bottom types : null and undefined . ... ', 'Fact is you will need to deal with both. ... ', 'Recommend == null to check for both undefined or null . ... ', 'One exception, root level undefined values which we discuss next.', 'Remember how I said you should use == null .']
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A: The difference between a NULL and a Zero-Length String (ZLS) is that a NULL has no value, whereas a ZLS has been specifically given a value of blank. It's basically the difference between saying, "no value" or "no value YET."
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There's no null in Python. Instead, there's None. As stated already, the most accurate way to test that something has been given None as a value is to use the is identity operator, which tests that two variables refer to the same object. In Python, to represent an absence of the value, you can use a None value (types.
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2 Answers. A null pointer just means the pointer isn't pointing to anything, or in some languages means it is unknown what it is pointing at. ... A dangling pointer is one that you think is pointing at something but in reality is no longer there, hence the pointer is actually inaccurate but doesn't know it.
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You cannot set attributes on NULL. So by definition NULL is very different to zero length vectors. A zero length vector very much isn't absent. ... A zero-length pairlist is NULL, as would be expected in Lisp but in contrast to a zero-length list.
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permalink #instance_variable_get(symbol) ⇒ Object Returns the value of the given instance variable, or nil if the instance variable is not set. The @ part of the variable name should be included for regular instance variables.
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SQL SERVER – Explanation and Comparison of NULLIF and ISNULL. Returns a null value if the two specified expressions are equal. ... NULLIF is equivalent to a searched CASE function in which the two expressions are equal and the resulting expression is NULL.
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Null has no bounds, it can be used for string, integer, date, etc. fields in a database. Empty string is just regarding a string; it's a string like 'asdfasdf' is, but is just has no length.