Vesa Karvonen

Added `attrsOr`, `attrs`, and `object`

1

See [question on Gitter](https://gitter.im/calmm-js/chat?at=5afe87fad245fe2eb7bdadf2).

WIP to relax type predicates for objects and array-likes

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Closes #127 * [ ] Consider changing `seemsArrayLike` to require that `length` is not an own enumerable property

One very common pattern I see in code using traversals is uses of `L.when` to filter elements based on some field: ```js L.when(x => x.type === 'something') ``` The condition...

* [ ] Maps [draft code](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAFgQwgWQKZTiAJjAvDAW3Ux1wD4YAPPCsAVwBsGYBCfagMg5igE8AHVCABmVANpEM2ALp5c+AOTC6YYFACW4BQChQkWIggBRMFABO61BDzwkaKVgAUC1KYtWFASl3hotiADi6DaG9iTOAOboXto++jBYIAAiqAzoqDaOANYANISeNDCOBAB0WKnp2Z55BN5xfvxmIPzICPw2WYWOlHkA+nkAYnmU6gBMvAMF5DADJQRtjtq8XSrlwupgqKTyMLzaAPxFhibmlhDdBYeJKWlQqNl5mwDuMK38FwUAXDCrqOubWG832erwWxzcZwuMEO1G+AEkSggzGYELwAAyeEoQdAPKiearaEbjAaOQxBKBQmElKIUrJfH5gNYbLZ5Ol1PR+LBNfgAOXAAAUEOozNZ2IUEeoIABBZGoqFcKglNJgCIYOT4UbQqgwb6-f5bWIc2CuU5WN6ZHowdSDYZjCZTCiLcGm86UbyHWbzd5WQogt6OKwEgAyJQqBHOMpRvBKwiaBAueWtMzy3UTDpmcwWXOafLAguFEFtxNTVvx+O031mIg+ht8sAAbggGHQzW0bCGoCABio1JowI4xCb3Cg2nkAIzSbxGmBZVC8EftfAdrs9jTgAdDs5vPJoyexBggCKOGAhmmORrNf0KSheR6oF7+sRia8KcdoieTgreA9Hk9YnEXi0CwKLwt4wAALKMd4PgsT4vm+H74jA36HseIZmKgBAgPW9yAVeN7VDAfqwc+N4IdIn7IfuqF-lhWDqMIvADo2zatvweQhk8cCuI4ABK1IUmOaIYp40h5PxmwRAgdzQaC7xwWRMBCROeTPqBeSQRRSEob+6GYdh9xiCxLYLhxJRcTx-Gqo4QkiWJRH3nJA6ka+SnvvZamuZplGeEAA) * [ ] Sets [draft code](https://calmm-js.github.io/partial.lenses/playground.html#MYewdgzgLgBAFgQwgWQKZTiAJjAvDAW3Ux1wD4YAPPCsAVwBsGYBCfagMg5igE8AHVCABmVANpEM2ALp5c+AOTC6YYFACW4BQChQkWIggBRMFABO61BDzwkaKVgAUC1KYtWFASl3hotiAASSDaG9iTOhl7aPvowWCAAIqgM6Kg2jgDWADSEnjQwjgQAdFjJqZmeOQTeMX78ZiD8AMroNhn5jpQ5APo5AGI5lOoATLx9eeQwfUUECPyO2rwdvNoA-DBgqADuMC1QjoYm5pYQnXnr1ABcMACSRQhmZgi8AAye91hOGd7XB0hH7lOlHOcUSZSgqEyOU2Oz2Zzy1xUpWE6k2WE8lW0Q1GfT+gSQZxgFyKhgqMERYGRqNQWBy3xqej8ADcEAw6FY9ukujB1P1BiMxhMKAtDm4Tmc1lMZnNOtZJjDduhZZUYAAZIplAinACCj2eRWEDQIZxyvKm-JxGO012mInh0QYIAA5o41UUnUr6o04QpKF5odtFfsxL6FNIMTBvI6XW6Pfsvc0lQpeP6NoG4SG-eG8lHna71RBPQ1E-tk6nzOyA7ClZmwxHczGC0XvUmUyrhKzC1Wg45a9nI9po-mioX48WfX7253UN2M6H+w3h2ZUAQQEzIQmJ6mFXOs-WHXm3ausOphLxeyy2Rz0Dl1Vs4K5HAAld37ACMLzenmkORfmydCAQrONYfm+OQACzDAug6Huqy6ruuF6suyEB7LeRT3o+L5Ou+n4Yj+abVsGoEQVB9ZAA)

Partial isomorphisms make it possible to define both parsers and stringifiers (or even [pretty printers](https://github.com/polytypic/prettier-printer/)) simultaneously as noted in e.g. [Invertible syntax descriptions: Unifying parsing and pretty printing](http://www.informatik.uni-marburg.de/~rendel/unparse/). It might...

Document main performance considerations

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There should a section in the documentation that explains main performance considerations when using lenses. - [x] Warn about reconstruction of optics in `L.choose` - [x] Explain that nesting traversals...

Switch playground to use e.g. Monaco editor

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Currently the playground uses [Klipse](https://github.com/viebel/klipse) which uses [CodeMirror](https://codemirror.net/). It works fine, but an editor like [Monaco](https://microsoft.github.io/monaco-editor/index.html) could fairly easily be configured to provide completion and online documentation.