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RE: One-based indexes in XPath

Subject: RE: One-based indexes in XPath
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Tue, 20 May 2008 18:05:03 +0100
RE:  One-based indexes in XPath
Because the language was designed for users, not for programmers, and users
still have this old-fashioned habit of referring to the first chapter in a
book as Chapter One. (Though I did once hear Dijkstra refer to the fourth
slide in someone's presentation as the third.)

(I fully agree that when handling tables, or subscripting into strings,
zero-based addressing would often be much more convenient. There are
arguments both ways, and as always, I can't tell you what the actual history
of the decision was; I can only post-rationalize it.)

Michael Kay

> -----Original Message-----
> From: Justin Johansson [mailto:procode@xxxxxxxxxxx] 
> Sent: 20 May 2008 18:15
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  One-based indexes in XPath
> Trusting this question is relevant to the XSL List.
> Would someone please give me advice as to why "1-based" 
> indexes are used in XPath, such as para[1] instead of para[0] 
> for the first para item/element?
> Why does the spec for XPath (and its/XQuery operator/function 
> library) go against the norm for modern programming languages 
> in which zero is the base for array-like collections?
> The reason for my question is to do with reconciling XPath 
> and XSLT with an implementation in Javascript in which zero 
> is the base index for arrays.
> My users may well be perplexed by having to decide whether an 
> index number is in XPath/XSLT-world or Javascript-world.
> Thanks for comments,
> Justin Johansson

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