neitzels irrelevant irregular intarweb notes

Martin groks the L: (Level At)

Ten days ago, I made my first REST queries using the shell.

Two days later, I tried the same queries with J. This turned out to be quite easy because two addons do all the work:

   require 'web/gethttp convert/json'
   j =. gethttp 'https://atlas.ripe.net/api/v2/probes/2871'

   _60 ]\ j
{"prefix_v4":"217.13.64.0/20","status":{"since":"2018-06-13T
04:35:32Z","id":1,"name":"Connected"},"prefix_v6":"2a00:1030
::/32","description":"GDS Marshlabs","last_connected":152912
2097,"tags":[{"name":"DSL","slug":"dsl"},{"name":"Home","slu
g":"home"},{"name":"No NAT","slug":"no-nat"},{"name":"IPv6 T
unnel","slug":"ipv6-tunnel"},{"name":"dual-stack","slug":"du
al-stack"},{"name":"IPv4","slug":"ipv4"},{"name":"IPv6","slu
g":"ipv6"},{"name":"system: V2","slug":"system-v2"},{"name":
"system: Resolver Mangles Case","slug":"system-resolver-mang
les-case"},{"name":"system: IPv4 Works","slug":"system-ipv4-
works"},{"name":"system: IPv6 Works","slug":"system-ipv6-wor
ks"},{"name":"Native IPv4","slug":"native-ipv4"},{"name":"sy
stem: IPv4 Capable","slug":"system-ipv4-capable"},{"name":"s
ystem: IPv6 Capable","slug":"system-ipv6-capable"},{"name":"
system: IPv6 Stable 1d","slug":"system-ipv6-stable-1d"},{"na
me":"system: IPv4 Stable 1d","slug":"system-ipv4-stable-1d"}
],"geometry":{"type":"Point","coordinates":[10.5215,52.2675]
},"type":"Probe","address_v6":"2a00:1030:100:0:220:4aff:fee0
:2212","address_v4":"217.13.64.149","total_uptime":190721773
,"country_code":"DE","is_public":true,"id":2781,"asn_v4":249
56,"asn_v6":24956,"status_since":1528864532,"first_connected
":1333468450,"is_anchor":false}                             

   _ 3 {. dec_json j
┌──────────────┬───────────────────────────────────┬──────────────┐
│prefix_v4     │status                             │prefix_v6     │
├──────────────┼───────────────────────────────────┼──────────────┤
│217.13.64.0/20│┌────────────────────┬──┬─────────┐│2a00:1030::/32│
│              ││since               │id│name     ││              │
│              │├────────────────────┼──┼─────────┤│              │
│              ││2018-06-13T04:35:32Z│1 │Connected││              │
│              │└────────────────────┴──┴─────────┘│              │
└──────────────┴───────────────────────────────────┴──────────────┘

So the json decoder turns syntactical markup into equivalent nested boxed data in the J world.

The J primitives dealing with such nested boxes are

1. L. Level Of
2. L: Level At
3. {:: Map/Fetch
4. S: Spread

Time to dig deeper into these. I spent a few hours until I really understood why, for example,

   |.  L:1  ] _ 3 {. dec_json j
┌──────────────┬───────────────────────────────────┬──────────────┐
│4v_xiferp     │sutats                             │6v_xiferp     │
├──────────────┼───────────────────────────────────┼──────────────┤
│02/0.46.31.712│┌────────────────────┬──┬─────────┐│23/::0301:00a2│
│              ││2018-06-13T04:35:32Z│1 │Connected││              │
│              │├────────────────────┼──┼─────────┤│              │
│              ││since               │id│name     ││              │
│              │└────────────────────┴──┴─────────┘│              │
└──────────────┴───────────────────────────────────┴──────────────┘

As of now, I am missing the flexibility of the { From selectors with the very rigid {:: Fetch paths. Some blend would be nice.

Also, I am still marvelling at possibilities of dyadic L: applications:

   a
┌───┬──────────────────┐
│1 2│┌────┬───────────┐│
│   ││abcd│0 1 2 3 4 5││
│   │└────┴───────────┘│
└───┴──────────────────┘
   c
┌─────┬─────┐
│┌───┐│┌───┐│
││ABC│││DEF││
│└───┘│└───┘│
└─────┴─────┘

   a ;L:0 c
┌───────────┬──────────────────────────────┐
│┌─────────┐│┌──────────┬─────────────────┐│
││┌───┬───┐│││┌────┬───┐│┌───────────┬───┐││
│││1 2│ABC│││││abcd│DEF│││0 1 2 3 4 5│DEF│││
││└───┴───┘│││└────┴───┘│└───────────┴───┘││
│└─────────┘│└──────────┴─────────────────┘│
└───────────┴──────────────────────────────┘
   a ;L:1 c
┌─────────┬────────────────────────┐
│┌───┬───┐│┌──────────────────┬───┐│
││1 2│ABC│││┌────┬───────────┐│DEF││
│└───┴───┘│││abcd│0 1 2 3 4 5││   ││
│         ││└────┴───────────┘│   ││
│         │└──────────────────┴───┘│
└─────────┴────────────────────────┘

Maybe I'll do less extra boxing for enabling each as in

   (;:'foo bar')  ,each  <'extraboxhere'
┌───────────────┬───────────────┐
│fooextraboxhere│barextraboxhere│
└───────────────┴───────────────┘

and employ L: instead in the future:

   (;:'foo bar')  ,L:0  'noextraboxhere'
┌─────────────────┬─────────────────┐
│foonoextraboxhere│barnoextraboxhere│
└─────────────────┴─────────────────┘

We'll see.