Upgrade to Pro — share decks privately, control downloads, hide ads and more …

First-Class Commands, the 2017 Edition

First-Class Commands, the 2017 Edition

NDC Oslo June 15, 2017

Reg Braithwaite

June 15, 2017
Tweet

More Decks by Reg Braithwaite

Other Decks in Technology

Transcript

  1. class Buffer { constructor (text = '') { this.text =

    text; } replaceWith (replacement, from = 0, to = this.text.length) { this.text = this.text.slice(0, from) + replacement + this.text.slice(to); return this; } toString () { return this.text; } } © 2017 Reginald Braithwaite. Some rights reserved. 6
  2. let buffer = new Buffer(); buffer.replaceWith( "The quick brown fox

    jumped over the lazy dog" ); buffer.replaceWith("fast", 4, 9); buffer.replaceWith("canine", 40, 43); //=> The fast brown fox jumped over the lazy canine © 2017 Reginald Braithwaite. Some rights reserved. 7
  3. we can treat methods as first- class entities © 2017

    Reginald Braithwaite. Some rights reserved. 11
  4. what does it mean to treat an invocation as a

    first-class entity? © 2017 Reginald Braithwaite. Some rights reserved. 13
  5. class Edit { constructor (buffer, {replacement, from, to}) { this.buffer

    = buffer; Object.assign(this, {replacement, from, to}); } doIt () { this.buffer.text = this.buffer.text.slice(0, this.from) + this.replacement + this.buffer.text.slice(this.to); return this.buffer; } } © 2017 Reginald Braithwaite. Some rights reserved. 15
  6. class Buffer { constructor (text = '') { this.text =

    text; } replaceWith (replacement, from = 0, to = this.text.length) { return new Edit(this, {replacement, from, to}); } toString () { return this.text; } } © 2017 Reginald Braithwaite. Some rights reserved. 16
  7. let buffer = new Buffer(), jobQueue = []; jobQueue.push( buffer.replaceWith(

    "The quick brown fox jumped over the lazy dog" ) ); jobQueue.push( buffer.replaceWith("fast", 4, 9) ); jobQueue.push( buffer.replaceWith("canine", 40, 43) ); while (jobQueue.length > 0) { jobQueue.shift().doIt(); } //=> The fast brown fox jumped over the lazy canine © 2017 Reginald Braithwaite. Some rights reserved. 17
  8. class Edit { netChange () { return this.from - this.to

    + this.replacement.length; } } © 2017 Reginald Braithwaite. Some rights reserved. 21
  9. let buffer = new Buffer(); buffer.replaceWith( "The quick brown fox

    jumped over the lazy dog" ).netChange(); //=> 44 buffer.replaceWith("fast", 4, 9).netChange(); //=> -1 © 2017 Reginald Braithwaite. Some rights reserved. 22
  10. class Edit { reversed () { let replacement = this.buffer.text.slice(this.from,

    this.to), from = this.from, to = from + this.replacement.length; return new Edit(buffer, {replacement, from, to}); } } © 2017 Reginald Braithwaite. Some rights reserved. 28
  11. let buffer = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); let doer = buffer.replaceWith("fast", 4, 9), undoer = doer.reversed(); doer.doIt(); //=> The fast brown fox jumped over the lazy dog undoer.doIt(); //=> The quick brown fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 29
  12. class Buffer { constructor (text = '') { this.text =

    text; this.history = []; this.future = []; } } © 2017 Reginald Braithwaite. Some rights reserved. 31
  13. class Buffer { replaceWith (replacement, from = 0, to =

    this.length()) { let doer = new Edit(this, {replacement, from, to}), undoer = doer.reversed(); this.history.push(undoer); this.future = []; return doer.doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 32
  14. class Buffer { undo () { let undoer = this.history.pop(),

    redoer = undoer.reversed(); this.future.unshift(redoer); return undoer.doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 34
  15. let buffer = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); buffer.replaceWith("fast", 4, 9) //=> The fast brown fox jumped over the lazy dog buffer.replaceWith("canine", 40, 43) //=> The fast brown fox jumped over the lazy canine © 2017 Reginald Braithwaite. Some rights reserved. 35
  16. buffer.undo() //=> The fast brown fox jumped over the lazy

    dog buffer.undo() //=> The quick brown fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 36
  17. class Buffer { redo () { let redoer = this.future.shift(),

    undoer = redoer.reversed(); this.history.push(undoer); return redoer.doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 38
  18. buffer.redo() //=> The fast brown fox jumped over the lazy

    dog buffer.redo() //=> The fast brown fox jumped over the lazy canine © 2017 Reginald Braithwaite. Some rights reserved. 39
  19. invocations as first-class entities: we stored them; we queried them;

    we transformed them. © 2017 Reginald Braithwaite. Some rights reserved. 41
  20. class Buffer { replaceWith (replacement, from = 0, to =

    this.length()) { let doer = new Edit(this, {replacement, from, to}), undoer = doer.reversed(); this.history.push(undoer); this.future = []; return doer.doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 43
  21. why do we have to throw the future away? ©

    2017 Reginald Braithwaite. Some rights reserved. 44
  22. class Buffer { replaceWith (replacement, from = 0, to =

    this.length()) { let doer = new Edit(this, {replacement, from, to}), undoer = doer.reversed(); this.history.push(undoer); // this.future = []; return doer.doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 45
  23. let buffer = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); buffer.replaceWith("fast", 4, 9); //=> The fast brown fox jumped over the lazy dog buffer.undo(); //=> The quick brown fox jumped over the lazy dog buffer.replaceWith("My", 0, 3); //=> My quick brown fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 46
  24. "My qfastbrown fox jumped over the lazy dog" © 2017

    Reginald Braithwaite. Some rights reserved. 48
  25. let buffer = new Buffer("The quick brown fox jumped over

    the lazy dog"); "The quick brown fox jumped over the lazy dog" // PAST // FUTURE © 2017 Reginald Braithwaite. Some rights reserved. 51
  26. buffer.replaceWith("fast", 4, 9) "The fast brown fox jumped over the

    lazy dog" // PAST replaceWith("fast", 4, 9) // FUTURE © 2017 Reginald Braithwaite. Some rights reserved. 52
  27. buffer.undo() "The quick brown fox jumped over the lazy dog"

    // PAST // FUTURE replaceWith("fast", 4, 9) © 2017 Reginald Braithwaite. Some rights reserved. 53
  28. buffer.replaceWith("My", 0, 3) "My quick brown fox jumped over the

    lazy dog" // PAST replaceWith("My", 0, 3) // FUTURE replaceWith("fast", 4, 9) © 2017 Reginald Braithwaite. Some rights reserved. 54
  29. buffer.redo() "My qfastbrown fox jumped over the lazy dog" //

    PAST replaceWith("My", 0, 3) replaceWith("fast", 4, 9) // FUTURE © 2017 Reginald Braithwaite. Some rights reserved. 55
  30. every command depends on the history of commands preceding it

    © 2017 Reginald Braithwaite. Some rights reserved. 56
  31. prepending a command into its history alters the command ©

    2017 Reginald Braithwaite. Some rights reserved. 57
  32. let buffer = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); let fast = new Edit( buffer, { replacement: "fast", from: 4, to: 9 } ); let my = new Edit( buffer, { replacement: "My", from: 0, to: 3 } ); © 2017 Reginald Braithwaite. Some rights reserved. 58
  33. let buffer = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); let fast = new Edit( buffer, { replacement: "fast", from: 4, to: 9 } ); let my = new Edit( buffer, { replacement: "My", from: 0, to: 3 } ); © 2017 Reginald Braithwaite. Some rights reserved. 59
  34. class Edit { isBefore (other) { return other.from >= this.to;

    } } fast.isBefore(my); //=> false my.isBefore(fast); //=> true © 2017 Reginald Braithwaite. Some rights reserved. 60
  35. class Edit { prependedWith (other) { if (this.isBefore(other)) { return

    this; } else if (other.isBefore(this)) { let change = other.netChange(), {replacement, from, to} = this; from = from + change; to = to + change; return new Edit(this.buffer, {replacement, from, to}) } } } © 2017 Reginald Braithwaite. Some rights reserved. 61
  36. class Buffer { replaceWith (replacement, from = 0, to =

    this.length()) { let doer = new Edit(this, {replacement, from, to}), undoer = doer.reversed(); this.history.push(undoer); this.future = this.future.map( (edit) => edit.prependedWith(doer) ); return doer.doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 64
  37. let buffer = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); buffer.replaceWith("fast", 4, 9); //=> The fast brown fox jumped over the lazy dog buffer.undo(); //=> The quick brown fox jumped over the lazy dog buffer.replaceWith("My", 0, 3); //=> My quick brown fox jumped over the lazy dog buffer.redo(); © 2017 Reginald Braithwaite. Some rights reserved. 66
  38. "My fast brown fox jumped over the lazy dog" ©

    2017 Reginald Braithwaite. Some rights reserved. 67
  39. what did fixing redo teach us about invocations as first-

    class entities? © 2017 Reginald Braithwaite. Some rights reserved. 68
  40. "People assume that time is a strict progression of cause

    to effect, but actually from a non- linear, non-subjective viewpoint— it's more like a big ball of wibbly wobbly… time-y wimey… stuff." © 2017 Reginald Braithwaite. Some rights reserved. 69
  41. reversed() and prependedWith() show us we can change both the

    direction and order of time. © 2017 Reginald Braithwaite. Some rights reserved. 70
  42. let alice = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); let bob = new Buffer( "The quick brown fox jumped over the lazy dog" ); © 2017 Reginald Braithwaite. Some rights reserved. 72
  43. for simplicity, we'll omit undo , redo and reversed class

    Buffer { constructor (text = '') { this.text = text; this.history = []; } } © 2017 Reginald Braithwaite. Some rights reserved. 73
  44. class Buffer { replaceWith (replacement, from = 0, to =

    this.length()) { let edit = new Edit(this, {replacement, from, to} ); this.history.push(edit); return edit.doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 74
  45. alice.replaceWith("My", 0, 3); //=> My quick brown fox jumped over

    the lazy dog bob.replaceWith("fast", 4, 9); //=> The fast brown fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 75
  46. class Buffer { append (theirEdit) { this.history.forEach( (myEdit) => {

    theirEdit = theirEdit.prependedWith(myEdit); }); return new Edit(this, theirEdit).doIt(); } } © 2017 Reginald Braithwaite. Some rights reserved. 77
  47. class Buffer { appendAll(otherBuffer) { otherBuffer.history.forEach( (theirEdit) => this.append(theirEdit) );

    return this; } } © 2017 Reginald Braithwaite. Some rights reserved. 78
  48. alice.appendAll(bob); //=> My fast brown fox jumped over the lazy

    dog bob.appendAll(alice); //=> My fast brown fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 79
  49. let GUID = () => ??? class Buffer { constructor

    (text = '', history = []) { let befores = new Set(history.map(e => e.guid)); history = history.slice(0); Object.assign(this, {text, history, befores}); } share () { return new Buffer(this.text, this.history); } } © 2017 Reginald Braithwaite. Some rights reserved. 82
  50. class Edit { constructor (buffer, { guid = GUID(), befores

    = new Set(), replacement, from, to }) { this.buffer = buffer; befores = new Set(befores); Object.assign(this, {guid, replacement, from, to, befores}); } } © 2017 Reginald Braithwaite. Some rights reserved. 83
  51. class Buffer { has (edit) { return this.befores.has(edit.guid); } perform

    (edit) { if (!this.has(edit)) { this.history.push(edit); this.befores.add(edit.guid); return edit.doIt(); } } } © 2017 Reginald Braithwaite. Some rights reserved. 84
  52. class Buffer { replaceWith (replacement, from = 0, to =

    this.length()) { let befores = this.befores, let edit = new Edit(this, {replacement, from, to, befores} ); return this.perform(edit); } } © 2017 Reginald Braithwaite. Some rights reserved. 85
  53. class Buffer { append (theirEdit) { this.history.forEach( (myEdit) => {

    theirEdit = theirEdit.prependedWith(myEdit); }); return this.perform(new Edit(this, theirEdit)); } } © 2017 Reginald Braithwaite. Some rights reserved. 86
  54. class Buffer { appendAll(otherBuffer) { otherBuffer.history.forEach( (theirEdit) => this.has(theirEdit) ||

    this.append(theirEdit) ); return this; } } © 2017 Reginald Braithwaite. Some rights reserved. 87
  55. class Edit { prependedWith (other) { if (this.isBefore(other) || this.befores.has(other.guid)

    || this.guid === other.guid) return this; let change = other.netChange(), {guid, replacement, from, to, befores} = this; from = from + change; to = to + change; befores = new Set(befores); befores.add(other.guid); return new Edit(this.buffer, {guid, replacement, from, to, befores}); } } © 2017 Reginald Braithwaite. Some rights reserved. 88
  56. let alice = new Buffer( "The quick brown fox jumped

    over the lazy dog" ); let bob = alice.share(); //=> The quick brown fox jumped over the lazy dog alice.replaceWith("My", 0, 3); //=> My quick brown fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 90
  57. let carol = alice.share(); //=> My quick brown fox jumped

    over the lazy dog bob.replaceWith("fast", 4, 9); //=> The fast brown fox jumped over the lazy dog alice.appendAll(bob); //=> My fast brown fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 91
  58. bob.appendAll(alice); //=> My fast brown fox jumped over the lazy

    dog alice.replaceWith("spotted", 8, 13); //=> My fast spotted fox jumped over the lazy dog bob.appendAll(alice); //=> My fast spotted fox jumped over the lazy dog carol.appendAll(bob); //=> My fast spotted fox jumped over the lazy dog © 2017 Reginald Braithwaite. Some rights reserved. 92
  59. "Unfortunately, implementing OT sucks. There's a million algorithms with different

    tradeoffs, mostly trapped in academic papers. The algorithms are really hard and time consuming to implement correctly." © 2017 Reginald Braithwaite. Some rights reserved. 93
  60. perhaps we should borrow a trick from react, and periodically

    scan a "shadow buffer" for diffs that we exchange with collaborators… © 2017 Reginald Braithwaite. Some rights reserved. 94
  61. how does differential synchronization differ from the command pa!ern? ©

    2017 Reginald Braithwaite. Some rights reserved. 96
  62. this is a very big problem space © 2017 Reginald

    Braithwaite. Some rights reserved. 97
  63. class Buffer { replaceWith () { ... } share ()

    { ... } append () { ... } appendAll () { ... } } © 2017 Reginald Braithwaite. Some rights reserved. 99
  64. class Branch { commit () { ... } fork ()

    { ... } cherryPick () { ... } merge () { ... } } © 2017 Reginald Braithwaite. Some rights reserved. 100
  65. with invocations as first-class entities, we can build distributed algorithms

    and protocols; we can master time and change © 2017 Reginald Braithwaite. Some rights reserved. 102