Preoccupation with zero, empty strings, empty elements, emptyeverything

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

When was the last time you went to the store to purchase zero oranges?

When was the last time you created an XML document to have zero elements?

Those are strange concepts, aren't they?

Zero is a strange concept. 

Roughly 1500 years after the introduction of zero as a number by mathematicians in India, the concept is still not well accepted in computer science:

	- Many programming languages do not 
	  support records with zero fields

	- Many programming languages do not 
	  support arrays with zero elements

	- Many programming languages do not 
	  support variable definitions with zero 
	  variables

	- In some programming languages the 
	  syntax for calling a routine with zero 
	  parameters differs from that for a 
	  routine with one or more parameters

	- XML has a special syntax for empty 
	  elements

	- Many compilers refuse to compile a 
	  module that defines zero names

	- No parser generator can produce a 
	  parser for the empty language (the 
	  language with zero strings)

This preoccupation with empty strings, sets, languages, etc. is not frivolous, since it is well-known that the ease with which a system handles empty cases is a measure of its cleanliness and robustness.

Most (not all) of the above is from the book: "Parsing Techniques" by Grune and Jacobs.

/Roger