Added % operator for table construction

[zevv]

% is essentially the same thing as toTable, but allows for a more concise notation:

var a = %{"key_1": "value_1", "key_2": "value_2"}

I don't expect this PR to go through as-is because the % operator might be confused with the Json constructor, although it does not actually clash.

[mrhdias]

This syntax is similar to that used in perl. The developers already know this syntax for arrays and hashs.

var a = @[1, 2, 3] # like @arrays in perl
var h = %{"key_1": "value_1", "key_2": "value_2"} # like %hashes in perl

[timotheecour]

I find toTable more readable / searchable and less likely to be confused with existing %, more generally I usually prefer explicit names to operators (except for commonly accepted operator names) ; a module can always define its own alias operator

I don't expect this PR to go through as-is because the % operator might be confused with the Json constructor, although it does not actually clash.

it does:

 Error: ambiguous call; both tables.%(pairs: openarray[tuple of (A, B)]) [declared in /Users/timothee/git_clone/nim/Nim_temp2/lib/pure/collections/tables.nim(326, 6)] and json.%(elements: openarray[T]) [declared in /Users/timothee/git_clone/nim/Nim_temp2/lib/pure/json.nim(333, 6)] match for: (array[0..1, tuple of (string, string)])
    var a = %{"key_1": "value_1", "key_2": "value_2"}

import tables
import json

proc main()=
  var a = %{"key_1": "value_1", "key_2": "value_2"}
  echo a

main()

[juancarlospaco]

Seems confusing with the JSON one. 🤔 Maybe another operator, maybe on the Sugar module.

[Araq]

Well, sorry, rejected. JSON already took the %. And in general we don't add new crazy operators anymore.