map:merge

Creates a new map that combines entries from a number of existing maps. There is one entry in the new map for each distinct key present in the union of the input maps; the way duplicate keys are handled is determined by the supplied $options.

merge($maps as map(*)*) ➔ map(*)

merge($maps as map(*)*, $options as map(*)) ➔ map(*)

Namespace

http://www.w3.org/2005/xpath-functions/map

Links to W3C specifications

XPath 3.1 Functions and Operators

XSLT 3.0 Specification

Notes on the Saxon implementation

From 9.9.1, two new vendor-defined options are recognized, and together can be used to explicitly indicate that the new optimized implementation of maps (DictionaryMap) should be used for the resulting merged map. The option 'key-type':'string' constrains the entries in the map to be strings (a dynamic error occurs if not), and 'final':true() indicates that the map should be constructed assuming no map:put() or map:remove() calls will take place (if they do, they will work, but will result in the whole map being copied).

XPath 3.1 version implemented since Saxon 9.7.

Signature changed to add $options argument from 9.7.0.8, with one recognized option 'duplicates':'reject'|'use-first'|'use-last'|'combine'|'unspecified'. For full details see the specification.

From 9.7.0.8, there is a change to the default behaviour of the function when there are duplicate keys. Previously, the associated value for each key in the new map was taken from the last map in the input sequence containing that key. From 9.7.0.8, the default behaviour is to take the value from the first map containing that key. See the warning above.

From 9.7.0.10, the option 'duplicates':'unspecified' is renamed 'duplicates':'use-any' (but 'unspecified' is retained as a synonym).

Available as defined in XSLT 3.0 since Saxon 9.6; in XSLT, XPath, and XQuery, whether or not 3.0 is available.

This function replaces the function map:new() defined in previous working drafts of XSLT 3.0, which was available in Saxon 9.4 to 9.6.