[xsl] Converting a sequence of xs:string to a map

["Christophe Marchand christophe@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Hello !

I leave my legacy job, so I now use my personal mail address...

I have a sequence of xs:string : ('amount', 'vat-rate', 'total')
And I want a map where keys are the labels from the sequence, and values are
the position of label in sequence : { 'amount': 1, 'vat-rate': 2, 'total': 3}

Any help will be much appreciated, as my XPath is very rustyB  !
Thanks in advance,
Christophe