# Extensions

The extension functions `saxon:index()` and `saxon:find()` have been changed. These functions allow creation of a user-defined index over a sequence, and fast retrieval of items from the sequence by using the index. The function `saxon:index()` no longer returns the sequence in question, rather it now defines an object of type `{http://saxon.sf.net/java-type}com.saxonica.extra.IndexedSequence` which can be used only as input to the `saxon:find()` function. The `saxon:find()` function now has a one-argument version which returns the sequence in question. This change has been made for robsustness: the existing design was proving excessively difficult to maintain.

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