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I know that NULL isn't necessary in a programming language, and I recently made the decision not to include NULL in my programming language. Declaration is done by initialization, so it is impossible to have an uninitialized variable. My hope is that this will eliminate the NullPointerException in favor of more meaningful exceptions or simply not having certain kinds of bugs.
Of course, since the language is implemented in C, there will be NULLs used under the covers.
My question is, besides using NULL as an error flag (this is handled with exceptions) or as an endpoint for data structures such as linked lists and binary trees (this is handled with discriminated unions) are there any other use-cases for NULL for which I should have a solution? Are there any really important implications of not having NULL which could cause me problems?
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NULL values are used to indicate that you could have a value, but you don't know what that value should be yet. They are placeholders until you finally collect the data needed to fill the table field with a real value. You should never confuse NULL values for zeros or blank strings.
It states that the corresponding value is either unknown or undefined. It is different from zero or "". They should be avoided to avoid the complexity in select & update queries and also because columns which have constraints like primary or foreign key constraints cannot contain a NULL value.
In computer programming, null is both a value and a pointer. Null is a built-in constant that has a value of zero. It is the same as the character 0 used to terminate strings in C. Null can also be the value of a pointer, which is the same as zero unless the CPU supports a special bit pattern for a null pointer.
While undefined has been in existence since the creation of coding, null is the misguided invention of British computer scientist Tony Hoare (most famous for his Quicksort algorithm) in 1964, who coined his invention of null references as his “billion dollar mistake”.
There's a recent article referenced on LtU by Tony Hoare titled Null References: The Billion Dollar Mistake which describes a method to allow the presence of NULLs in a programming language, but also eliminates the risk of referencing such a NULL reference. It seems so simple yet it's such a powerful idea.
Update: here's a link to the actual paper that I read, which talks about the implementation in Eiffel: http://docs.eiffel.com/book/papers/void-safety-how-eiffel-removes-null-pointer-dereferencing
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