From b5b9ae6772da0956945b783f68a9cd5442828aa4 Mon Sep 17 00:00:00 2001
From: Vesa Karvonen <vesa.a.j.k@gmail.com>
Date: Fri, 19 Oct 2018 08:35:56 +0300
Subject: [PATCH] Added "Your mental model of optics - shattered"

---
 docs/mental-optics/index.html | 81 +++++++++++++++++---------------
 docs/mental-optics/slides.md  | 87 +++++++++++++++++++----------------
 2 files changed, 91 insertions(+), 77 deletions(-)

diff --git a/docs/mental-optics/index.html b/docs/mental-optics/index.html
index aebe535..e34aba0 100644
--- a/docs/mental-optics/index.html
+++ b/docs/mental-optics/index.html
@@ -30,14 +30,6 @@
 still left mysterious, please <a href="https://gitter.im/calmm-js/chat">let me know</a> and
 I&#39;ll try to add some additional notes.</p>
 </aside></script></section><section  data-markdown><script type="text/template">
-## Outline
-
-* Part I - Motivation ❓
-* Part II - Basics 💡
-* Part III - Examples 😮
-* Part IV - Exercises 💪
-* Part V - Wrap up 🎓
-</script></section><section  data-markdown><script type="text/template">
 ## Part I - Motivation
 </script></section><section  data-markdown><script type="text/template">
 > My mental model of lenses is that of a path into a data structure. — A
@@ -96,20 +88,12 @@
 <!-- .element: class="fragment" -->Optics are a *game changer*
 
 <aside class="notes"><p>We&#39;ll actually not be going too much into theory in the presentation, but
-the other claims will definitely be addressed.</p>
-</aside></script></section><section  data-markdown><script type="text/template">
-## Disclaimer
-
-* This will not be a theory lesson
-* This isn't a complete treatment
-* You will not know everything after this training
-
-<aside class="notes"><p>When presenting a topic, I have a tendency to try to mention a lot of
-related details for completeness.  I have decided leave such things out of this
-presentation.  So, if you find that e.g. I didn&#39;t mention some related
-generalization or list full set of related concepts, then most likely that is
-because I made a decision to leave that out due to desire to keep the
-presentation shorter.</p>
+the other claims will definitely be addressed.  When presenting a topic, I have
+a tendency to try to mention a lot of related details for completeness.  I have
+decided leave such things out of this presentation.  So, if you find that e.g. I
+didn&#39;t mention some related generalization or list full set of related concepts,
+then most likely that is because I made a decision to leave that out due to
+desire to keep the presentation shorter.</p>
 </aside></script></section><section  data-markdown><script type="text/template">
 ## Part II - Basics
 </script></section><section  data-markdown><script type="text/template">
@@ -119,8 +103,8 @@
 > structure in some particular way and then put it back together.
 
 *<span class="fragment">Traversals,</span> <span class="fragment">Lenses,</span> <span class="fragment">Isomorphisms,</span> <span class="fragment">..., Getters</span>*
-
-<!-- .element: class="fragment" -->[Taking apart an
+</script></section><section  data-markdown><script type="text/template">
+[Taking apart an
 object](https://calmm-js.github.io/partial.lenses/playground.html#PTAEBUEMGsEsDsDmpIAdICcAuL6gPYBGAVgKYDGOCoAtgK4A2WsqDpoAJrAGbekal4OAO6QAngGcAUFPL54EnB0hZIoALygA3gA8AXKADkkQwBpQYg4cJnQALyvlDAXxkgAMgDpEpLAApDHVtlVQBKKQ9PCV8AoPNDAEEk4JVIcMiBGnwAN1JYlLCI4C8ffy9oUjFSDnMQtKKvaP8AbXLK6vMABi6AXXiAMQB5QYL6yLkGNko-L0EsDFhSCVrU9OLvGK80VjEEss85haXzLwFcjGjQlcLIpr9Wz22GXf3DxeXQU9Jzy-iTPqMAHVIBIALRxTirBqeCZTfYVSTXMbrGgIWD0GgzTwIj51NZeYj4BABUG2NqIyE3FH4LjcMRYnHmABKMPk5BUAX6+HwpKulORXlhFH22UgDDox35+M8WVp9K8ovFkpZcng7P8hgAQpheUjpaUsVwJISEP4ERoAHygc3qW1GIKgAD8RkImEMoCs3G5hj5eOhBq8qAw+FQEny8TEPr1-s2niDIYkAFEdORSKgNRDDJHfVDIgGZdsEIg-H4dOYxOY7KFLaBmrpy5XnOZmmXtBX7M4ej0c1TPH2gA)
 &mdash; [with
 narrative](https://calmm-js.github.io/partial.lenses/playground.html#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-fxAy0TBSjAB1MEAWmanA1EQSqI4tFZPBO8dA4qlMrlHsekmDDK1WzAAGF8LLYyPzb21MrIAG7VKaAhYPQaE6F2PNRPtWB8Bhk-hhXQsOxN-Bt3QaNDQAupcR8AgAvXbATR82Q0f4hPM832oBdjUqRQVSQDcu3ZPcnjVUBtmleRyBUAJKXwfAvyDP9xxiBJT07NkChfOpBxBJ1FjtOgfTww8ANbadZyHUBqIYWjF2RC4rVXct1zqBYSKomi6OQuR4DQ-xDAAIUwHCD2PAgzyE7seT2B1Gi8LgJBAoQ-BHDQAD5nyeDR1E0QJDFAAB+IxCEwayrG4LDDFw95wgGVhxUOUZmDSQokx0vScAkOhCBxWYbm8LTPH1VAJFWFoxDcxSAJ1AECHgBgCjUCRcnIHhYHIUAwoioZ8BhVEgS5LBNI9eKJAAUR0VJUGkptDBS9yW02DLAVIG0xGKBBkFIVrSHaiCCqKkqypxeqnRoF1Rr8PwdHMMRzDscJ1BM3FdE27bnHMXENu0Lb7GcMkyR6kNmTQGrYywIKeD4AQhFK5U6EoOgBGuTxAbcMAayKFQeXRTIGHERBSngDsOD2eRIJUALIeKFRzEGwRQBcs8wvIHixWFNgnsoUxrnUgQUGp+AH34M4MlESRArY3VSovdh0GwZTYWwDJKr7HAkT5HJmHICRPEpyk-uKfgFgELHIEJp9ilFdhmYySHCFgLgBEoWB5Dtcw7QYfBhFGrL2Be0B4HwaNsrESmUyvdgMRoXwikt7hskfOW2YBcxCCvFAGAxVnVPZdTlNgRAEDtMm6oSEWpnFTwgA)
@@ -199,12 +183,14 @@
 R.chain(R.values, data)
 
 L.collect([L.elems, L.values], data)
+//        ^^^^^^^^^^^^^^^^^^^
 ```
 
 ```js
 R.map(R.map(R.toUpper), data)
 
 L.modify([L.elems, L.values], R.toUpper, data)
+//       ^^^^^^^^^^^^^^^^^^^
 ```
 
 Optic composition is constant when the selection of elements is constant.
@@ -222,12 +208,14 @@
 R.join('-', R.chain(R.values, data))
 
 L.join('-', [L.elems, L.values], data)
+//          ^^^^^^^^^^^^^^^^^^^
 ```
 
 ```js
 R.sum(R.chain(R.values, data))
 
 L.sum([L.elems, L.values], data)
+//    ^^^^^^^^^^^^^^^^^^^
 ```
 
 No intermediate collection is computed by traversals.
@@ -250,6 +238,21 @@
 
 The above is incomplete!
 </script></section><section  data-markdown><script type="text/template">
+## To manipulate data
+
+1. <!-- .element: class="fragment" -->Compose an optic to select the desired elements
+   * <!-- .element: class="fragment" -->Write some draft optic
+   * <!-- .element: class="fragment" -->Test by querying with it
+     ```js
+     L.collect  L.get
+     ```
+   * <!-- .element: class="fragment" -->Iterate
+2. <!-- .element: class="fragment" --> Apply the operation you wanted
+   ```
+   L.modify L.set L.remove L.sum L.foldl L.sum ...
+   ```
+3. <!-- .element: class="fragment" -->Go home and spend time with family
+</script></section><section  data-markdown><script type="text/template">
 ### express so much with so little
 
 <img src="rivero.png">
@@ -480,11 +483,9 @@
   keys](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBvAUAUwB4IC2AlmEseAMIhw4BcMA5AMoBMADAIwAcjANLgKFqtBowASASX5ZEATxH0YYAK4AbNQIjAAFiBBqAcisIAjHACcGndlwEqADoig4AKsUJLGHHgFp2AJz+ATIAjio40BSQDADaAESc8Xww8azJqQDM8QC6WlAqtGBQEHFYGABmxBbQhkSRYpIQIDJqCLX1DPEACupQUMTJWBAQYGJcE5z+Npwy0IU4xcZmltYC4ZED4KUwsRhwxBAObXLL5lapSSnaIBY4AGoIahEMmQC+KfuHxwinJuddbLXUB3R7PJQAFjeeWGIJwzBMDAA7B9ylUalA6p4dowALIqaAIVrtTGdVK4hAAa0pCAsCCGIzGTHYHFZ-lZcwKRUx-1WMFY6wiUW2cS+RxOZz5aQyN1BTxeMChnwO4t+kou8SBMFlD3lSlY0K0cIRhAYADZUTksG8sFhQJBYFA6ZA2i40DAADIAOkICAcDlIAHMIAAKWJYWKMfBEUjkKg0HD8JgFKCU0hQECUyzIRgwyPR4QJpOMSkgRN5xjyRTFkAQIkV7R6Azq4ul9QqVSeCwtCuOZxuDyJlKMWkAN1rLmeYG6ABPiKOZ4QZzOLDPcwJIxthZBW3IIHJCHJKRAcFB1xHGPNuRBW5mcG0kOfI+iOtji6eO4OzxW2q+h0wIBUSlPxIJ9Ly5RYeRWCxbyzX9O0sHsN0rb4JV5GDh0pPcDz3MCdTBCJiwDaAcFPPDjRMIjDhcYgihNX1cywHIAEogA)
   &mdash; [with
   narrative](https://calmm-js.github.io/partial.lenses/playground.html#PTAECEFMBsHsHdQEsDOoWwLaVJghgCY4CuADqAXgC56gBGeKkBosAdqLQGawBO+VUFQAW1ZGmJMWSNlUi82eaNACeyDnjYAoEJwDGVYks6lS0JHupJ2AOlCgA6qMHxIAchbmA1jiqwK-qhC-lS8mig8-ELCOJQ0wfSQOmCQAB6kfHIEdqAAKv4EIc6griWagn5CYWwo0NS+MaA+KmiwXNE4sHQAVpAGaJUAYjJsqMLJnGwsShgUvLDkIjgABigobMugpPOk8lRIkCgANImWkg04aRm8WaCRAriSgmywVBMyetDERNFipHg3CzEOq8LYHPSddpxPA2LRaPTsFCCaGgAC8oAA3lo0nhMDIrOwAMKwIgALlAbgAygAmAAMAEYABxuI7Y1K44lkikACQAkiytJQVJzIOS2MDoKyUHphLBYNAAHLETB0eTk+m0hmsshxSC5JDYcluOlMgC0tIAnOaLQKAI7EQ77RHkgDaACJ6W6Tm7qV7QG6AMxugC6UsMRFkKFdWgxXCQvCRCtxhyNvIwArqieT5LdAAVgVR9l6tGs2EaGRX6eaNfSBUjvpBZEqVWrQPTWfbHdYaq6MQRUGY8Cpm6reDnPSdpXxIAA1JQO8kBgC+Jz7A7qw+Vo5zQcnCN4s-notAABYl6GS-vIJTleSAOwrmNxhNUJPYKMUgCyTzwGcYr+zf1PzwLwvABPBi1Lcs6Rg80YLrcNG1fLdW2pDsHSRbsPxdNcUEHTcWzHf1fT3ac5y+Y8z1Xfs8I3EdW0DP0pwPciF1AalzylK8b0wckADZH2DLQlzhXRuXkHAgk0cQsD4UhhFQTBfgqapanqNAuHmJSlnUOQFGMRR33UUAAFE2AAc3MFBhGCCY0j0xRoFAQzDmM4Y2FGazYXhREVPCOo5DRUAABkbHwUwZHMlAAAoXS0F03BxPFFCdNgRRZClDCoLwZD8Hwbl-C8EqS9KTjcLxYHcIqPCHUqKVgFBCtZBLpVleV6N4DLytgYFiHFbB5jcaqdXqfVsC6gEADcGrkL42FzAATpBJoWzAFoW3gFqG5q3E7TDES6rwWhUTAVC8JgqG2+K3HrCMqBQQ7YB8OpqCuhLnyzd8usgQxRmwS7qszADxrKlBiC8PqDSQN6bsQpsUM6sqKuexh+vkWAYZo-COsO47Toe6rmMPCiutIVA5B+mGiZ40nycgJAIx4-Ahq0YMAEpRLAQY+FAJKzFFOFQvMn7otCfz6lB7jlTcDmJgVV4GjEJYD3EZyQlUgLuzuHnVnWZYcgAQQ0QtIEwUgKnV8XAt1jYJminnNDUV4YlBPqrNuSajzZrZ5gIYgITQZY+qIOM2GYZZSU5oWRbFmoAsgUH1hlznQEpWATllRBChKXwNfqDomkgFoAH57GCym0ARM2GpwWgxcm+RGqckQxHMyrWgb3gJiUZvGmaNAZE4ZzHWYChqFoJFeH9wwVbaTheDCFpJhYLpen6SOfJqQR+5MzuVHgF2cHRUK6gALxUaKDz0NEAD4QpsBEpmi+KACUbFQaKDYXoc2ZOF1QpgKbY4oAr7BiKm-D+AB5HofQqC-1AP-GwSFeAHGAQA6AQCTihSQFwEy0AmDRWigAfROEgb2qI75IDRKidEtI-6hhAX0NmYCtBs1lroNOJxuhPASJ3HBKgTgYMugMXgahlihQRMoWBmxKhMAuIXFoG8QASPlBggw0Ud57wPhJE40J2FgHyKAPQB587SVQLJXg8lFLKSqFbVyPcC79xOKUSwHAXiIG4UiEwZgVATB0ssWOak5CbHMZgOSCkUBKTEA4nSPA9DnFaO0fxmj5D70PssPxYRO5Nw3o-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)
-  &mdash;
-  [structurally](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBvAUAUwB4IC2AlmEseAMIhw4BcMA5AMoBMADAIwAcjANLgKFqtBowASASX5ZEATxH0YYAK4AbNQIjAAFiBBqAcisIAjHACcGndlwEqADoig4AKsUJLGHHgFp2AJz+ATIAjio40BSQDADaAESc8Xww8azJqQDM8QC6WlAqtGBQEHFYGABmxBbQhkSRYpIQIDJqCLX1DPEACupQUMTJWBAQYGJcE5z+Npwy0IU4xcZmltYC4ZED4KUwsRhwxBAObXLL5lapSSnaIBY4AGoIahEMmQC+KfuHxwinJuddbLXUB3R7PJQAFjeeWGIJwzBMDAA7B9ylUalA6p4dowALIqaAIVrtTGdVK4hAAa0pCAsCCGIzGTHYHFZ-lZcwKRUx-1WMFY6wiUW2cS+RxOZz5aQyN1BTxeMChnwO4t+kou8SBMFlD3lSlY0K0cIRhAYADZUTksG8sFhQJBYA47gBzOkHMDOpogNAwAAyADoHMRgJSABTYApQSmkKAgSmWZBifBEUjkKg0HAySkgLzJ4QZmQgCAIMTyRRZkDqFSqTwWEBibR6AzqmS0gBuRZczzA3QAJ8Q273CL3exZe2JHM43B5MwJKXIIHJCHJKRAcFAxBthZAK-G2kgyox5tyIDIA7S6XJQ1gA0GQ+HcAUwDON0x0R1sXMVJTqx5iGI2g-WcsGzPd2hrSx6yYY9Fh5FYLBkNsnhIQkkIAQQsDtoBwZ44kYLcth3FJzwsS9Q1vYMwwwGB50XZccRVH4-ng-gYCDbD1wbOEwQiRgYDeABKASYXYlxiCKE1CBLaDjRMRhrQErBFKtQTbQDZ111DJ0cFdBB3U9ZoUmcBABKAA)
+  &mdash; [structurally](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBvAUAUwB4IC2AlmEseAMIhw4BcMA5AMoBMADAIwAcjANLgKFqtBowASASX5ZEATxH0YYAK4AbNQIjAAFiBBqAcisIAjHACcGndlwEqADoig4AKsUJLGHHgFp2AJz+ATIAjio40BSQDADaAESc8Xww8azJqQDM8QC6WlAqtGBQEHFYGABmxBbQhkSRYpIQIDJqCLX1DPEACupQUMTJWBAQYGJcE5z+Npwy0IU4xcZmltYC4ZED4KUwsRhwxBAObXLL5lapSSnaIBY4AGoIahEMmQC+KfuHxwinJuddbLXUB3R7PJQAFjeeWGIJwzBMDAA7B9ylUalA6p4dowALIqaAIVrtTGdVK4hAAa0pCAsCCGIzGTHYHFZ-lZcwKRUx-1WMFY6wiUW2cS+RxOZz5aQyN1BTxeMChnwO4t+kou8SBMFlD3lSlY0K0cIRhAYADZUTksG8sFhQJBYA47gBzOkHMDOpogNAwAAyADoHMRgJSABTYApQSmkKAgSmWZBifBEUjkKg0HAySkgLzJ4QZmQgCAIMTyRRZkDqFSqTwWEBibR6AzqmS0gBuRZczzA3QAJ8Q273CL3exZe2JHM43B5MwJKXIIHJCHJKRAcFAxBthZAK-G2kgyox5tyIDIA7S6XJQ1gA0GQ+HcAUwDON0x0R1sXMVJTqx5iGI2g-WcsGzPd2hrSx6yYY9Fh5FYLBkNsnhIQkkIAQQsDtoBwZ44kYLcth3FJzwsS9Q1vYMwwwGB50XZccRVH4-ng-gYCDbD1wbOEwQiRgYDeABKASYXYlxiCKE1CBLaDjRMRhrQErBFKtQTbQDZ111DJ0cFdBB3U9ZoUmcBABKAA)
 
-* [Parsing and pretty-printing
-  combinators](https://calmm-js.github.io/partial.lenses/playground.html#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-bBQq5EwutLLtty0I4jrUBPLlXrdIm56yiCp6gr0iqUEBp6Ym+66DgPOa5S4ABHPoMEVKtAbmYT5MOhaltei7RpQbLQm2wQ7IhzafGIDAyjVCZqFwYQOAarbhBokg0AiZ8KZQUxGdIFngMhmSCCQg7myOiYBAEIgOAk20uHtIhHWAAM3SY4B41TeyuuO7L9stUIdCFmF6nqesgrweqicw8k1QyDnUKZ7mYia04YlJ16ZFhwRFRiOCEIwT22QILFFEMEwzAsKwKSpdR+0ZQJmVZL4bFcROk+cOmfB6NkiEYbs1XJUp4MEJ0TxDYANsw4kCDQIx8ICMa0E8NmmgALw6n1HNz62oVt58DVzh2YHGHH7u1xECH6IWR9WTJykqcz6jBQ3QAntEbu6SQ0Ez7s017wVcY1ofWHCQ79ezNZ40SeogpRLfJhhuHHVzr2C-qbMNlADxFpwSzq4EWvPBiB-84YBfqrQshZS5JXfjAT+Qhv7PmpPXEIEwm4t3eu3BmNsubd1kNvfEpwDR3RytrKikhFigB2Hsd6R19b6AXvMUh9Q7wL3Id9a0GRp5cFnk0FoXkSEEBiMwjEN1sE3zdvDLgoQAHe2zDQ1+6d15Z0npIp+jDX6QOgRwWBv9aKFmtDg3ewtB6EIPuELYfxpCULhKY0ASMZhSD+jMMxdihETGphLAhWtjFvB9nSNgFivExABEFNhFQOENG2gvfxPjWDLyBLIIywjnZ4zghXKuWw4F120XFcBsouGMA4EQHOpQ-ahDUV-NJWiiwgHkBmLMuT8nxn0HEUAd5QD6HJi0ppj0Xrn0SEAA)
+* [Parsing and pretty-printing combinators](https://calmm-js.github.io/partial.lenses/playground.html#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-bBQq5EwutLLtty0I4jrUBPLlXrdIm56yiCp6gr0iqUEBp6Ym+66DgPOa5S4ABHPoMEVKtAbmYT5MOhaltei7RpQbLQm2wQ7IhzafGIDAyjVCZqFwYQOAarbhBokg0AiZ8KZQUxGdIFngMhmSCCQg7myOiYBAEIgOAk20uHtIhHWAAM3SY4B41TeyuuO7L9stUIdCFmF6nqesgrweqicw8k1QyDnUKZ7mYia04YlJ16ZFhwRFRiOCEIwT22QILFFEMEwzAsKwKSpdR+0ZQJmVZL4bFcROk+cOmfB6NkiEYbs1XJUp4MEJ0TxDYANsw4kCDQIx8ICMa0E8NmmgALw6n1HNz62oVt58DVzh2YHGHH7u1xECH6IWR9WTJykqcz6jBQ3QAntEbu6SQ0Ez7s017wVcY1ofWHCQ79ezNZ40SeogpRLfJhhuHHVzr2C-qbMNlADxFpwSzq4EWvPBiB-84YBfqrQshZS5JXfjAT+Qhv7PmpPXEIEwm4t3eu3BmNsubd1kNvfEpwDR3RytrKikhFigB2Hsd6R19b6AXvMUh9Q7wL3Id9a0GRp5cFnk0FoXkSEEBiMwjEN1sE3zdvDLgoQAHe2zDQ1+6d15Z0npIp+jDX6QOgRwWBv9aKFmtDg3ewtB6EIPuELYfxpCULhKY0ASMZhSD+jMMxdihETGphLAhWtjFvB9nSNgFivExABEFNhFQOENG2gvfxPjWDLyBLIIywjnZ4zghXKuWw4F120XFcBsouGMA4EQHOpQ-ahDUV-NJWiiwgHkBmLMuT8nxn0HEUAd5QD6HJi0ppj0Xrn0SEAA)
 
 * [Flattening a
   tree](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBtAUAbyyASzgC4YBGAGi2AAsCAbOAJwFMxTsdCSYAmCmLQbM2HLkVIBmAUMat2mALoBfFVXE8ALDLpzRS5VkVZl6-BJgBWKrJELO3UgDYdw+RzW5HMAOyu99hqkABz+dh6qhsZRWNTg0DAAZvRIUGwEYADmAEoArvQsEGgwADIAdAj0aUxgSAQAboUAFFjlALYIAA6dGZlNIGgAfJg4ZWMgYe4GAhij4wKdEBGKigCUVNjtXT1ZTU3AEAIgq0MjY2UTgrrhghCmmJcHK+utZQBeBJ0A6gRQNGQtLbdXp7ToyBYQE6oYbYDBgmBzMrABYIeRQJYwRaqdTnZGYjFwgTnRYqIyrLDkxQbV65LJMEC5ToAIQAnk1yrRCMBmhgAOSLXkCAAMAl53F5VJgYqIvNWL3KqKYCBZEHZZQ6wN2-QhUJhiMuWIE+pRaIxWLWlIpsXKmRYUBamwqUDSbU6UAAoo0mCyAKqdJrJVLpLJ5AqQqhUrCIZAUoA)
@@ -521,14 +522,11 @@
 </script></section><section  data-markdown><script type="text/template">
 ## Limitation: Single data structure
 
-* <!-- .element: class="fragment" -->But perhaps there are ways...
-* <!-- .element: class="fragment" -->Laziness? (Works in read direction.)
-* <!-- .element: class="fragment" -->Some sort of cross product or join
-  combinator?
-* <!-- .element: class="fragment" -->Or use isomorphism combinators to massage
-  data?
-* <!-- .element: class="fragment" -->Extend optics to address multiple data
-  structures at once?
+* But perhaps there are ways...
+* Laziness? (Works in read direction.)
+* Some sort of cross product or join combinator?
+* Or use isomorphism combinators to massage data?
+* Extend optics to address multiple data structures at once?
 * <!-- .element: class="fragment" -->Somewhat open question (to me)
 </script></section><section  data-markdown><script type="text/template">
 ## When might I recommend to use optics?
@@ -595,7 +593,16 @@
 
 <!-- .element: class="fragment" -->Ask questions and request feedback.
 </script></section><section  data-markdown><script type="text/template">
-## What about Partial Lenses?
+## What about [Partial Lenses](https://github.com/calmm-js/partial.lenses/)?
+
+<small>(The lib used in these slides.)</small>
+
+* Fairly comprehensive API
+* Lots of interactive documentation
+* High test coverage
+* Been in production use since beginning
+* Optimized to some degree
+* Engineered for DCE
 
 <!-- .element: class="fragment" -->I **_can't_** recommend it, because...
 
diff --git a/docs/mental-optics/slides.md b/docs/mental-optics/slides.md
index f8579bc..e660e9f 100644
--- a/docs/mental-optics/slides.md
+++ b/docs/mental-optics/slides.md
@@ -16,16 +16,6 @@ I'll try to add some additional notes.
 
 ---
 
-## Outline
-
-* Part I - Motivation ❓
-* Part II - Basics 💡
-* Part III - Examples 😮
-* Part IV - Exercises 💪
-* Part V - Wrap up 🎓
-
----
-
 ## Part I - Motivation
 
 ---
@@ -94,22 +84,12 @@ years ago.
 <!-- .element: class="fragment" -->Optics are a *game changer*
 
 Note: We'll actually not be going too much into theory in the presentation, but
-the other claims will definitely be addressed.
-
----
-
-## Disclaimer
-
-* This will not be a theory lesson
-* This isn't a complete treatment
-* You will not know everything after this training
-
-Note: When presenting a topic, I have a tendency to try to mention a lot of
-related details for completeness.  I have decided leave such things out of this
-presentation.  So, if you find that e.g. I didn't mention some related
-generalization or list full set of related concepts, then most likely that is
-because I made a decision to leave that out due to desire to keep the
-presentation shorter.
+the other claims will definitely be addressed.  When presenting a topic, I have
+a tendency to try to mention a lot of related details for completeness.  I have
+decided leave such things out of this presentation.  So, if you find that e.g. I
+didn't mention some related generalization or list full set of related concepts,
+then most likely that is because I made a decision to leave that out due to
+desire to keep the presentation shorter.
 
 ---
 
@@ -124,7 +104,9 @@ presentation shorter.
 
 *<span class="fragment">Traversals,</span> <span class="fragment">Lenses,</span> <span class="fragment">Isomorphisms,</span> <span class="fragment">..., Getters</span>*
 
-<!-- .element: class="fragment" -->[Taking apart an
+---
+
+[Taking apart an
 object](https://calmm-js.github.io/partial.lenses/playground.html#PTAEBUEMGsEsDsDmpIAdICcAuL6gPYBGAVgKYDGOCoAtgK4A2WsqDpoAJrAGbekal4OAO6QAngGcAUFPL54EnB0hZIoALygA3gA8AXKADkkQwBpQYg4cJnQALyvlDAXxkgAMgDpEpLAApDHVtlVQBKKQ9PCV8AoPNDAEEk4JVIcMiBGnwAN1JYlLCI4C8ffy9oUjFSDnMQtKKvaP8AbXLK6vMABi6AXXiAMQB5QYL6yLkGNko-L0EsDFhSCVrU9OLvGK80VjEEss85haXzLwFcjGjQlcLIpr9Wz22GXf3DxeXQU9Jzy-iTPqMAHVIBIALRxTirBqeCZTfYVSTXMbrGgIWD0GgzTwIj51NZeYj4BABUG2NqIyE3FH4LjcMRYnHmABKMPk5BUAX6+HwpKulORXlhFH22UgDDox35+M8WVp9K8ovFkpZcng7P8hgAQpheUjpaUsVwJISEP4ERoAHygc3qW1GIKgAD8RkImEMoCs3G5hj5eOhBq8qAw+FQEny8TEPr1-s2niDIYkAFEdORSKgNRDDJHfVDIgGZdsEIg-H4dOYxOY7KFLaBmrpy5XnOZmmXtBX7M4ej0c1TPH2gA)
 &mdash; [with
 narrative](https://calmm-js.github.io/partial.lenses/playground.html#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-fxAy0TBSjAB1MEAWmanA1EQSqI4tFZPBO8dA4qlMrlHsekmDDK1WzAAGF8LLYyPzb21MrIAG7VKaAhYPQaE6F2PNRPtWB8Bhk-hhXQsOxN-Bt3QaNDQAupcR8AgAvXbATR82Q0f4hPM832oBdjUqRQVSQDcu3ZPcnjVUBtmleRyBUAJKXwfAvyDP9xxiBJT07NkChfOpBxBJ1FjtOgfTww8ANbadZyHUBqIYWjF2RC4rVXct1zqBYSKomi6OQuR4DQ-xDAAIUwHCD2PAgzyE7seT2B1Gi8LgJBAoQ-BHDQAD5nyeDR1E0QJDFAAB+IxCEwayrG4LDDFw95wgGVhxUOUZmDSQokx0vScAkOhCBxWYbm8LTPH1VAJFWFoxDcxSAJ1AECHgBgCjUCRcnIHhYHIUAwoioZ8BhVEgS5LBNI9eKJAAUR0VJUGkptDBS9yW02DLAVIG0xGKBBkFIVrSHaiCCqKkqypxeqnRoF1Rr8PwdHMMRzDscJ1BM3FdE27bnHMXENu0Lb7GcMkyR6kNmTQGrYywIKeD4AQhFK5U6EoOgBGuTxAbcMAayKFQeXRTIGHERBSngDsOD2eRIJUALIeKFRzEGwRQBcs8wvIHixWFNgnsoUxrnUgQUGp+AH34M4MlESRArY3VSovdh0GwZTYWwDJKr7HAkT5HJmHICRPEpyk-uKfgFgELHIEJp9ilFdhmYySHCFgLgBEoWB5Dtcw7QYfBhFGrL2Be0B4HwaNsrESmUyvdgMRoXwikt7hskfOW2YBcxCCvFAGAxVnVPZdTlNgRAEDtMm6oSEWpnFTwgA)
@@ -215,12 +197,14 @@ In traditional APIs operation and selection are fused and often overloaded.
 R.chain(R.values, data)
 
 L.collect([L.elems, L.values], data)
+//        ^^^^^^^^^^^^^^^^^^^
 ```
 
 ```js
 R.map(R.map(R.toUpper), data)
 
 L.modify([L.elems, L.values], R.toUpper, data)
+//       ^^^^^^^^^^^^^^^^^^^
 ```
 
 Optic composition is constant when the selection of elements is constant.
@@ -240,12 +224,14 @@ and efficiently both select and carry out the desired operation.
 R.join('-', R.chain(R.values, data))
 
 L.join('-', [L.elems, L.values], data)
+//          ^^^^^^^^^^^^^^^^^^^
 ```
 
 ```js
 R.sum(R.chain(R.values, data))
 
 L.sum([L.elems, L.values], data)
+//    ^^^^^^^^^^^^^^^^^^^
 ```
 
 No intermediate collection is computed by traversals.
@@ -272,6 +258,23 @@ The above is incomplete!
 
 ---
 
+## To manipulate data
+
+1. <!-- .element: class="fragment" -->Compose an optic to select the desired elements
+   * <!-- .element: class="fragment" -->Write some draft optic
+   * <!-- .element: class="fragment" -->Test by querying with it
+     ```js
+     L.collect  L.get
+     ```
+   * <!-- .element: class="fragment" -->Iterate
+2. <!-- .element: class="fragment" --> Apply the operation you wanted
+   ```
+   L.modify L.set L.remove L.sum L.foldl L.sum ...
+   ```
+3. <!-- .element: class="fragment" -->Go home and spend time with family
+
+---
+
 ### express so much with so little
 
 <img src="rivero.png">
@@ -536,11 +539,9 @@ just use different algebras to build the result.
   keys](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBvAUAUwB4IC2AlmEseAMIhw4BcMA5AMoBMADAIwAcjANLgKFqtBowASASX5ZEATxH0YYAK4AbNQIjAAFiBBqAcisIAjHACcGndlwEqADoig4AKsUJLGHHgFp2AJz+ATIAjio40BSQDADaAESc8Xww8azJqQDM8QC6WlAqtGBQEHFYGABmxBbQhkSRYpIQIDJqCLX1DPEACupQUMTJWBAQYGJcE5z+Npwy0IU4xcZmltYC4ZED4KUwsRhwxBAObXLL5lapSSnaIBY4AGoIahEMmQC+KfuHxwinJuddbLXUB3R7PJQAFjeeWGIJwzBMDAA7B9ylUalA6p4dowALIqaAIVrtTGdVK4hAAa0pCAsCCGIzGTHYHFZ-lZcwKRUx-1WMFY6wiUW2cS+RxOZz5aQyN1BTxeMChnwO4t+kou8SBMFlD3lSlY0K0cIRhAYADZUTksG8sFhQJBYFA6ZA2i40DAADIAOkICAcDlIAHMIAAKWJYWKMfBEUjkKg0HD8JgFKCU0hQECUyzIRgwyPR4QJpOMSkgRN5xjyRTFkAQIkV7R6Azq4ul9QqVSeCwtCuOZxuDyJlKMWkAN1rLmeYG6ABPiKOZ4QZzOLDPcwJIxthZBW3IIHJCHJKRAcFB1xHGPNuRBW5mcG0kOfI+iOtji6eO4OzxW2q+h0wIBUSlPxIJ9Ly5RYeRWCxbyzX9O0sHsN0rb4JV5GDh0pPcDz3MCdTBCJiwDaAcFPPDjRMIjDhcYgihNX1cywHIAEogA)
   &mdash; [with
   narrative](https://calmm-js.github.io/partial.lenses/playground.html#PTAECEFMBsHsHdQEsDOoWwLaVJghgCY4CuADqAXgC56gBGeKkBosAdqLQGawBO+VUFQAW1ZGmJMWSNlUi82eaNACeyDnjYAoEJwDGVYks6lS0JHupJ2AOlCgA6qMHxIAchbmA1jiqwK-qhC-lS8mig8-ELCOJQ0wfSQOmCQAB6kfHIEdqAAKv4EIc6griWagn5CYWwo0NS+MaA+KmiwXNE4sHQAVpAGaJUAYjJsqMLJnGwsShgUvLDkIjgABigobMugpPOk8lRIkCgANImWkg04aRm8WaCRAriSgmywVBMyetDERNFipHg3CzEOq8LYHPSddpxPA2LRaPTsFCCaGgAC8oAA3lo0nhMDIrOwAMKwIgALlAbgAygAmAAMAEYABxuI7Y1K44lkikACQAkiytJQVJzIOS2MDoKyUHphLBYNAAHLETB0eTk+m0hmsshxSC5JDYcluOlMgC0tIAnOaLQKAI7EQ77RHkgDaACJ6W6Tm7qV7QG6AMxugC6UsMRFkKFdWgxXCQvCRCtxhyNvIwArqieT5LdAAVgVR9l6tGs2EaGRX6eaNfSBUjvpBZEqVWrQPTWfbHdYaq6MQRUGY8Cpm6reDnPSdpXxIAA1JQO8kBgC+Jz7A7qw+Vo5zQcnCN4s-notAABYl6GS-vIJTleSAOwrmNxhNUJPYKMUgCyTzwGcYr+zf1PzwLwvABPBi1Lcs6Rg80YLrcNG1fLdW2pDsHSRbsPxdNcUEHTcWzHf1fT3ac5y+Y8z1Xfs8I3EdW0DP0pwPciF1AalzylK8b0wckADZH2DLQlzhXRuXkHAgk0cQsD4UhhFQTBfgqapanqNAuHmJSlnUOQFGMRR33UUAAFE2AAc3MFBhGCCY0j0xRoFAQzDmM4Y2FGazYXhREVPCOo5DRUAABkbHwUwZHMlAAAoXS0F03BxPFFCdNgRRZClDCoLwZD8Hwbl-C8EqS9KTjcLxYHcIqPCHUqKVgFBCtZBLpVleV6N4DLytgYFiHFbB5jcaqdXqfVsC6gEADcGrkL42FzAATpBJoWzAFoW3gFqG5q3E7TDES6rwWhUTAVC8JgqG2+K3HrCMqBQQ7YB8OpqCuhLnyzd8usgQxRmwS7qszADxrKlBiC8PqDSQN6bsQpsUM6sqKuexh+vkWAYZo-COsO47Toe6rmMPCiutIVA5B+mGiZ40nycgJAIx4-Ahq0YMAEpRLAQY+FAJKzFFOFQvMn7otCfz6lB7jlTcDmJgVV4GjEJYD3EZyQlUgLuzuHnVnWZYcgAQQ0QtIEwUgKnV8XAt1jYJminnNDUV4YlBPqrNuSajzZrZ5gIYgITQZY+qIOM2GYZZSU5oWRbFmoAsgUH1hlznQEpWATllRBChKXwNfqDomkgFoAH57GCym0ARM2GpwWgxcm+RGqckQxHMyrWgb3gJiUZvGmaNAZE4ZzHWYChqFoJFeH9wwVbaTheDCFpJhYLpen6SOfJqQR+5MzuVHgF2cHRUK6gALxUaKDz0NEAD4QpsBEpmi+KACUbFQaKDYXoc2ZOF1QpgKbY4oAr7BiKm-D+AB5HofQqC-1AP-GwSFeAHGAQA6AQCTihSQFwEy0AmDRWigAfROEgb2qI75IDRKidEtI-6hhAX0NmYCtBs1lroNOJxuhPASJ3HBKgTgYMugMXgahlihQRMoWBmxKhMAuIXFoG8QASPlBggw0Ud57wPhJE40J2FgHyKAPQB587SVQLJXg8lFLKSqFbVyPcC79xOKUSwHAXiIG4UiEwZgVATB0ssWOak5CbHMZgOSCkUBKTEA4nSPA9DnFaO0fxmj5D70PssPxYRO5Nw3o-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)
-  &mdash;
-  [structurally](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBvAUAUwB4IC2AlmEseAMIhw4BcMA5AMoBMADAIwAcjANLgKFqtBowASASX5ZEATxH0YYAK4AbNQIjAAFiBBqAcisIAjHACcGndlwEqADoig4AKsUJLGHHgFp2AJz+ATIAjio40BSQDADaAESc8Xww8azJqQDM8QC6WlAqtGBQEHFYGABmxBbQhkSRYpIQIDJqCLX1DPEACupQUMTJWBAQYGJcE5z+Npwy0IU4xcZmltYC4ZED4KUwsRhwxBAObXLL5lapSSnaIBY4AGoIahEMmQC+KfuHxwinJuddbLXUB3R7PJQAFjeeWGIJwzBMDAA7B9ylUalA6p4dowALIqaAIVrtTGdVK4hAAa0pCAsCCGIzGTHYHFZ-lZcwKRUx-1WMFY6wiUW2cS+RxOZz5aQyN1BTxeMChnwO4t+kou8SBMFlD3lSlY0K0cIRhAYADZUTksG8sFhQJBYA47gBzOkHMDOpogNAwAAyADoHMRgJSABTYApQSmkKAgSmWZBifBEUjkKg0HAySkgLzJ4QZmQgCAIMTyRRZkDqFSqTwWEBibR6AzqmS0gBuRZczzA3QAJ8Q273CL3exZe2JHM43B5MwJKXIIHJCHJKRAcFAxBthZAK-G2kgyox5tyIDIA7S6XJQ1gA0GQ+HcAUwDON0x0R1sXMVJTqx5iGI2g-WcsGzPd2hrSx6yYY9Fh5FYLBkNsnhIQkkIAQQsDtoBwZ44kYLcth3FJzwsS9Q1vYMwwwGB50XZccRVH4-ng-gYCDbD1wbOEwQiRgYDeABKASYXYlxiCKE1CBLaDjRMRhrQErBFKtQTbQDZ111DJ0cFdBB3U9ZoUmcBABKAA)
+  &mdash; [structurally](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBvAUAUwB4IC2AlmEseAMIhw4BcMA5AMoBMADAIwAcjANLgKFqtBowASASX5ZEATxH0YYAK4AbNQIjAAFiBBqAcisIAjHACcGndlwEqADoig4AKsUJLGHHgFp2AJz+ATIAjio40BSQDADaAESc8Xww8azJqQDM8QC6WlAqtGBQEHFYGABmxBbQhkSRYpIQIDJqCLX1DPEACupQUMTJWBAQYGJcE5z+Npwy0IU4xcZmltYC4ZED4KUwsRhwxBAObXLL5lapSSnaIBY4AGoIahEMmQC+KfuHxwinJuddbLXUB3R7PJQAFjeeWGIJwzBMDAA7B9ylUalA6p4dowALIqaAIVrtTGdVK4hAAa0pCAsCCGIzGTHYHFZ-lZcwKRUx-1WMFY6wiUW2cS+RxOZz5aQyN1BTxeMChnwO4t+kou8SBMFlD3lSlY0K0cIRhAYADZUTksG8sFhQJBYA47gBzOkHMDOpogNAwAAyADoHMRgJSABTYApQSmkKAgSmWZBifBEUjkKg0HAySkgLzJ4QZmQgCAIMTyRRZkDqFSqTwWEBibR6AzqmS0gBuRZczzA3QAJ8Q273CL3exZe2JHM43B5MwJKXIIHJCHJKRAcFAxBthZAK-G2kgyox5tyIDIA7S6XJQ1gA0GQ+HcAUwDON0x0R1sXMVJTqx5iGI2g-WcsGzPd2hrSx6yYY9Fh5FYLBkNsnhIQkkIAQQsDtoBwZ44kYLcth3FJzwsS9Q1vYMwwwGB50XZccRVH4-ng-gYCDbD1wbOEwQiRgYDeABKASYXYlxiCKE1CBLaDjRMRhrQErBFKtQTbQDZ111DJ0cFdBB3U9ZoUmcBABKAA)
 
-* [Parsing and pretty-printing
-  combinators](https://calmm-js.github.io/partial.lenses/playground.html#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-bBQq5EwutLLtty0I4jrUBPLlXrdIm56yiCp6gr0iqUEBp6Ym+66DgPOa5S4ABHPoMEVKtAbmYT5MOhaltei7RpQbLQm2wQ7IhzafGIDAyjVCZqFwYQOAarbhBokg0AiZ8KZQUxGdIFngMhmSCCQg7myOiYBAEIgOAk20uHtIhHWAAM3SY4B41TeyuuO7L9stUIdCFmF6nqesgrweqicw8k1QyDnUKZ7mYia04YlJ16ZFhwRFRiOCEIwT22QILFFEMEwzAsKwKSpdR+0ZQJmVZL4bFcROk+cOmfB6NkiEYbs1XJUp4MEJ0TxDYANsw4kCDQIx8ICMa0E8NmmgALw6n1HNz62oVt58DVzh2YHGHH7u1xECH6IWR9WTJykqcz6jBQ3QAntEbu6SQ0Ez7s017wVcY1ofWHCQ79ezNZ40SeogpRLfJhhuHHVzr2C-qbMNlADxFpwSzq4EWvPBiB-84YBfqrQshZS5JXfjAT+Qhv7PmpPXEIEwm4t3eu3BmNsubd1kNvfEpwDR3RytrKikhFigB2Hsd6R19b6AXvMUh9Q7wL3Id9a0GRp5cFnk0FoXkSEEBiMwjEN1sE3zdvDLgoQAHe2zDQ1+6d15Z0npIp+jDX6QOgRwWBv9aKFmtDg3ewtB6EIPuELYfxpCULhKY0ASMZhSD+jMMxdihETGphLAhWtjFvB9nSNgFivExABEFNhFQOENG2gvfxPjWDLyBLIIywjnZ4zghXKuWw4F120XFcBsouGMA4EQHOpQ-ahDUV-NJWiiwgHkBmLMuT8nxn0HEUAd5QD6HJi0ppj0Xrn0SEAA)
+* [Parsing and pretty-printing combinators](https://calmm-js.github.io/partial.lenses/playground.html#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-bBQq5EwutLLtty0I4jrUBPLlXrdIm56yiCp6gr0iqUEBp6Ym+66DgPOa5S4ABHPoMEVKtAbmYT5MOhaltei7RpQbLQm2wQ7IhzafGIDAyjVCZqFwYQOAarbhBokg0AiZ8KZQUxGdIFngMhmSCCQg7myOiYBAEIgOAk20uHtIhHWAAM3SY4B41TeyuuO7L9stUIdCFmF6nqesgrweqicw8k1QyDnUKZ7mYia04YlJ16ZFhwRFRiOCEIwT22QILFFEMEwzAsKwKSpdR+0ZQJmVZL4bFcROk+cOmfB6NkiEYbs1XJUp4MEJ0TxDYANsw4kCDQIx8ICMa0E8NmmgALw6n1HNz62oVt58DVzh2YHGHH7u1xECH6IWR9WTJykqcz6jBQ3QAntEbu6SQ0Ez7s017wVcY1ofWHCQ79ezNZ40SeogpRLfJhhuHHVzr2C-qbMNlADxFpwSzq4EWvPBiB-84YBfqrQshZS5JXfjAT+Qhv7PmpPXEIEwm4t3eu3BmNsubd1kNvfEpwDR3RytrKikhFigB2Hsd6R19b6AXvMUh9Q7wL3Id9a0GRp5cFnk0FoXkSEEBiMwjEN1sE3zdvDLgoQAHe2zDQ1+6d15Z0npIp+jDX6QOgRwWBv9aKFmtDg3ewtB6EIPuELYfxpCULhKY0ASMZhSD+jMMxdihETGphLAhWtjFvB9nSNgFivExABEFNhFQOENG2gvfxPjWDLyBLIIywjnZ4zghXKuWw4F120XFcBsouGMA4EQHOpQ-ahDUV-NJWiiwgHkBmLMuT8nxn0HEUAd5QD6HJi0ppj0Xrn0SEAA)
 
 * [Flattening a
   tree](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAJgQygmBeGBtAUAbyyASzgC4YBGAGi2AAsCAbOAJwFMxTsdCSYAmCmLQbM2HLkVIBmAUMat2mALoBfFVXE8ALDLpzRS5VkVZl6-BJgBWKrJELO3UgDYdw+RzW5HMAOyu99hqkABz+dh6qhsZRWNTg0DAAZvRIUGwEYADmAEoArvQsEGgwADIAdAj0aUxgSAQAboUAFFjlALYIAA6dGZlNIGgAfJg4ZWMgYe4GAhij4wKdEBGKigCUVNjtXT1ZTU3AEAIgq0MjY2UTgrrhghCmmJcHK+utZQBeBJ0A6gRQNGQtLbdXp7ToyBYQE6oYbYDBgmBzMrABYIeRQJYwRaqdTnZGYjFwgTnRYqIyrLDkxQbV65LJMEC5ToAIQAnk1yrRCMBmhgAOSLXkCAAMAl53F5VJgYqIvNWL3KqKYCBZEHZZQ6wN2-QhUJhiMuWIE+pRaIxWLWlIpsXKmRYUBamwqUDSbU6UAAoo0mCyAKqdJrJVLpLJ5AqQqhUrCIZAUoA)
@@ -591,14 +592,11 @@ optics for unidirectional operations.
 
 ## Limitation: Single data structure
 
-* <!-- .element: class="fragment" -->But perhaps there are ways...
-* <!-- .element: class="fragment" -->Laziness? (Works in read direction.)
-* <!-- .element: class="fragment" -->Some sort of cross product or join
-  combinator?
-* <!-- .element: class="fragment" -->Or use isomorphism combinators to massage
-  data?
-* <!-- .element: class="fragment" -->Extend optics to address multiple data
-  structures at once?
+* But perhaps there are ways...
+* Laziness? (Works in read direction.)
+* Some sort of cross product or join combinator?
+* Or use isomorphism combinators to massage data?
+* Extend optics to address multiple data structures at once?
 * <!-- .element: class="fragment" -->Somewhat open question (to me)
 
 ---
@@ -679,7 +677,16 @@ shorter.
 
 ---
 
-## What about Partial Lenses?
+## What about [Partial Lenses](https://github.com/calmm-js/partial.lenses/)?
+
+<small>(The lib used in these slides.)</small>
+
+* Fairly comprehensive API
+* Lots of interactive documentation
+* High test coverage
+* Been in production use since beginning
+* Optimized to some degree
+* Engineered for DCE
 
 <!-- .element: class="fragment" -->I **_can't_** recommend it, because...