Amanda Ross WaxCylinderRevival

An introduction to recursion in XQuery

Created: Nov 28, 2017
Updated: Nov 29, 2017: Now covers transformation of XML documents

Recursion is a powerful programming technique, but the idea is simple: instead of performing a single operation, a function calls itself repeatedly to whittle through a larger task. In XQuery, recursion can be used to accomplish complex tasks on data that a plain FLWOR expression (which iterates through a sequence) cannot, such as transforming an entire XML document from one format into another, like TEI or DocBook into HTML, EPUB, LaTeX, or XSL-FO. Transforming a document is well-suited to recursion because each of the document's nodes may need to be examined and manipulated based on the node's type, name, and location in the document; and once a node has been processed, the transformation must continue processing the nodes' children and descendants until the deepest leaf node has been processed. But learning the technique of recursion is often hard for a beginning program

OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application:

	#! /usr/bin/env ruby

	# NOTE: Requires Ruby 2.1 or greater.

	# This script can be used to parse and dump the information from
	# the 'html/contact_info.htm' file in a Facebook user data ZIP download.
	#
	# It prints all cell phone call + SMS message + MMS records, plus a summary of each.
	#
	# It also dumps all of the records into CSV files inside a 'CSV' folder, that is created

	xquery version "3.1";

	declare namespace tei="http://www.tei-c.org/ns/1.0";

	import module namespace dates="http://xqdev.com/dateparser" at "xmldb:exist:///db/apps/twitter/modules/date-parser.xqm";

	declare function local:get-date-candidate-field($div) {
	let $head := normalize-space(string-join($div/tei:head[1]/node()[not(./self::tei:note)]))
	let $source-note := normalize-space(string-join($div//tei:note[@type='source']))
	let $body := normalize-space(string-join($div/tei:head/following-sibling::node()))

	<?xml version="1.0" encoding="UTF-8"?>
	<html xmlns="http://www.w3.org/1999/xhtml" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:xforms="http://www.w3.org/2002/xforms" xmlns:xs="http://www.w3.org/2001/XMLSchema"
	xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xxforms="http://orbeon.org/oxf/xml/xforms" xmlns:fr="http://orbeon.org/oxf/xml/form-runner" xmlns:res="http://www.w3.org/2005/sparql-results#"
	xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:nm="http://nomisma.org/id/" xmlns:foaf="http://xmlns.com/foaf/0.1/"
	xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:skos="http://www.w3.org/2004/02/skos/core#"
	xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#" xmlns:xsd="http://www.w3.org/2001/XMLSchema#" xmlns:un="http://www.owl-ontologies.com/Ontology1181490123.owl#"
	xmlns:atom="http://www.w3.org/2005/Atom" xmlns:nomisma="https://github.com/nomisma" xmlns:rdac="http://www.rdaregistry.info/Element