Shooting arrows fast and accurately

How to use XQuery arrow expressions for fun and profit.

Transcript

1. Shooting Arrows fast and accurately
2. Hi! I am Juri Leino GitHub: @line-o twitter: @line_o 2/55 — XML Prague 2020
3. arrow expressions 3/55 — XML Prague 2020
4. arrow expressions evaluation order A !" f(B, C) evaluates to f(A, B, C) 4/55 — XML Prague 2020
5. arrow expressions "hello Prague" !" upper-case() !" tokenize(" ") is the same as tokenize( upper-case( "hello Prague"), " ") 5/55 — XML Prague 2020
6. learnings 6/55 — XML Prague 2020
7. learnings 123 !" function ($a) { $a * $a } 7/55 — XML Prague 2020
8. learnings 123 !" (function ($a) { $a * $a })() 8/55 — XML Prague 2020
9. learnings (: 123 "# :) (function ($a) { $a * $a })(123) 9/55 — XML Prague 2020
10. learnings • (1 to 9) !" sum#1 • error • (1 to 9) !" sum(.) • error again • 'world' !" concat('hello ', ?) • anonymous function with arity 1 10/55 — XML Prague 2020
11. learnings (1, 2, 3) !" count() (: !$ 3 :) (1, 2, 3) ! count(.) (: !$ (1, 1, 1) :) 11/55 — XML Prague 2020
12. !"! A ! B A ! B ! C A !" B A !" B !" C 12/55 — XML Prague 2020
13. !"! A ! (.) !" B A ! f(.) !" B (A !" B) ! C 13/55 — XML Prague 2020
14. functional programming a quick recap 14/55 — Photo by Victor Xok on Unsplash -- XML Prague 2020
15. partial application 15/55 — XML Prague 2020
16. partial application declare function local:add ($a, $b) { $a + $b }; let $add16 !" local:add(?, 16) let $add48 !" local:add(48, ?) 16/55 — XML Prague 2020
17. partial application (2, 1, 3, 8) ! $add48(.) !" codepoints-to-string() (: !% "2138" :) 17/55 — XML Prague 2020
18. higher order functions functions parameterised by or returning a function 18/55 — XML Prague 2020
19. higher order functions • fn:function-arity#1 • fn:function-name#1 • fn:function-lookup#2 19/55 — XML Prague 2020
20. higher order functions • fn:apply#2 • fn:for-each#2 • fn:filter#2 • fn:sort#3 • fn:fold-left#3 • fn:fold-right#3 20/55 — XML Prague 2020
21. higher order functions (2, 1, 3, 8) !" for-each($add48) !" for-each($add16) !" codepoints-to-string() (: !% "BACH" :) 21/55 — XML Prague 2020
22. Gluten-free programming™ no flour (FLWOR) 22/55 — XML Prague 2020
23. Gluten-free programming™ replace for, let, order by, group by, where with for-each, sort, fold-left, filter 23/55 — XML Prague 2020
24. xbow 24/55 — XML Prague 2020
25. Like functx, but for arrow expressions ! Priscilla Walmsley 25/55 — XML Prague 2020
26. (numerical) Comparisons gt, ge, lt, le, eq 26/55 — XML Prague 2020
27. comparisons xbow:gt(5) (: "# function(xs:numeric) :) 1 "$ xbow:gt(5)() (: "# false() :) (1 to 9) "$ filter(xbow:gt(5)) (: "# (6, 7, 8, 9) :) 27/55 — XML Prague 2020
28. helpers take, last, to-sequence, to-array, sortBy, ascending, descending, for-each-index, map-reverse, 28/55 — XML Prague 2020
29. helpers (2, 1, 3, 8) !" xbow:descending() !" xbow:take(2) !" xbow:to-array() (: !% [8, 3] :) 29/55 — XML Prague 2020
30. helpers (6 to 9) !" xbow:for-each-index( function ($item, $pos) { [$pos, $item] }) (: !% ([1, 6], [2, 7], [3, 8], [4, 9]) :) 30/55 — XML Prague 2020
31. XML helpers wrap-element, wrap-each, filter-attributes, attributes-to-map... 31/55 — XML Prague 2020
32. reduce Boil a sequence down to a boolean 32/55 — XML Prague 2020
33. reduce (1, 2, 4) !" xbow:some(xbow:gt(1)) (: !$ true() :) (1, 2, 4) !" xbow:all(xbow:le(4)) (: !$ true() :) (1, 2, 4) !" xbow:none(xbow:gt(10)) (: !$ true() :) 33/55 — XML Prague 2020
34. reduce (1 to 10) !" xbow:group-by(xbow:even-odd(?)) (: returns :) map { "even": (2, 4, 6, 8, 10), "odd": (1, 3, 5, 7, 9), } 34/55 — XML Prague 2020
35. accessors A function retrieving a value from a (complex) item. 35/55 — XML Prague 2020
36. accessors $posts !" ( map { "views": 10 }, map { "views": 1 }, map { "views": 4922 }, map { "views": 16 }, map { "views": 345 } ) 36/55 — XML Prague 2020
37. accessors function ($post) { $post?views }, map:get(?, 'views'), xbow:pluck('views') 37/55 — XML Prague 2020
38. accessors $posts !" for-each(xbow:pluck('views')) !" filter(xbow:gt(10)) (: returns :) (16, 345, 4922) 38/55 — XML Prague 2020
39. accessors $posts !" for-each(xbow:pluck('views')) !" filter(xbow:gt(10)) !" avg() (: returns :) 1761 39/55 — XML Prague 2020
40. accessors $posts !" filter( xbow:gt(10, xbow:pluck('views')) (: returns :) ( map { "views": 16 }, map { "views": 4923 }, map { "views": 345 } ) 40/55 — XML Prague 2020
41. accessors [ <year n="2001" !", <year n="2020" !", <year n="1999" !" ] !# array:filter( xbow:gt(2000, function ($y) { xs:integer($y/@n) }) 41/55 — XML Prague 2020
42. combine Merge functions into one 42/55 — XML Prague 2020
43. xbow:combine $large-sequence "# for-each( $a ) "# for-each( $b ) "# for-each( $c ) $large-sequence "# for-each( xbow:combine(($a, $b, $c))) 43/55 — XML Prague 2020
44. categorize Clustering data by rules 44/55 — XML Prague 2020
45. categorize (: A set of rules :) let $post-view-rules #$ [ xbow:eq(0), (: no one :) xbow:le(10), (: just a few :) xbow:le(100), (: almost successful :) xbow:gt(100) (: successful posts :) ] 45/55 — XML Prague 2020
46. categorize (: And a data set :) $posts "# xbow:categorize( $post-view-rules, xbow:pluck('views')) (: returns :) [ (), (map { "views":"1" }), (map { "views":"10" }, map { "views":"16" }), (map { "views":"4923" }, map { "views":"345" }) ] 46/55 — XML Prague 2020
47. categorize (: we can now label those for human consumption :) $posts "# xbow:categorize( $post-view-rules, xbow:pluck('views')) "# xbow:label([ 'no one', 'just a few', 'almost successful', 'successful posts' ]) 47/55 — XML Prague 2020
48. categorize (: generate ten complex rules :) let $rules "# xbow:array-fill(10, function ($item, $ignore) { math:pow($item, 4) "% xbow:lt() }) return $posts "% xbow:categorize($rules, xbow:pluck('views')) 48/55 — XML Prague 2020
49. Readable Code 49/55 — XMLPrague 2020 – Photo by Markus Spiske on Unsplash
50. Language 50/55 — XMLPrague 2020 – Photo by Mark Rasmuson on Unsplash
51. evolution 51/55 — XMLPrague 2020 – Photo by erokism on Flickr (CC BY 2.0)
52. Take part in it! • xquery/XSLT 3.1 (2017) • github.com/expath/xpath-ng (2017) • xquery/XSLT 4 (?) 52/55 — XML Prague 2020
53. Cool things already proposed • if without else • structure decomposition • inline function syntax 53/55 — XML Prague 2020
54. What I would like to see • the discussion to continue • a process to extend and evolve xquery • select function by arity and type • async, await (over promises) • generators • tooling (!) 54/55 — XML Prague 2020
55. Thanks for having me; Go shoot some arrows! github.com/line-o/xbow 55/55 — XML Prague 2020