Feat/getting substring methods

[am-cid]

closes #246

---

new

• builtin String methods to get substrings (#246)

  1. first() takes in int, gets from the 0th char up to n.
  2. last() takes in int, gets last char up to n
  3. substr() takes two ints (n,m), gets from nth char up to mth char
  4. from() takes str (item), returns empty string if item is not in string. returns substring containing item up to end of the string
  5. upTo() takes str (item), returns empty string if item is not in string. returns substring containing beginning of string up to item

etc

• bugfix: did not type check ClassAccessor's id, only accessed

---

test log

sample text file
------------------------------------------
 1 |
 2 | fwunc mainuwu-san() [[
 3 |     a-senpai = "hello"~
 4 |     b-chan~
 5 |     b = a.first("").first(2,2).len()~
 6 |     b = a.last(2,2).len()~
 7 |     b = a.upTo(2,2).len()~
 8 |     b = a.from(2,2).len()~
 9 |     b = a.substr(2,2,2).len()~
10 |
11 | ]]
12 |
------------------------------------------
end of file

Call arg type mismatch:
        __________________________________________
          |
          |     'senpai.first()' called here
        5 |     b = a.first("").first(2,2).len()~
          |           ^^^^^
          |
          |     'senpai.first()' class method expects 1 argument
          |     EXPECTED     ACTUAL     ARG
          |     ✗ chan       senpai     ""
        __________________________________________

Call arg type mismatch:
        __________________________________________
          |
          |     'senpai.first()' called here
        5 |     b = a.first("").first(2,2).len()~
          |                     ^^^^^
          |
          |     'senpai.first()' class method expects 1 argument
          |     EXPECTED     ACTUAL     ARG
          |     ✓ chan       chan       2
          |
          |     1 arg too many
          |     ✗ NONE        ( 2 )      2
        __________________________________________

Call arg type mismatch:
        _______________________________
          |
          |     'senpai.last()' called here
        6 |     b = a.last(2,2).len()~
          |           ^^^^
          |
          |     'senpai.last()' class method expects 1 argument
          |     EXPECTED     ACTUAL     ARG
          |     ✓ chan       chan       2
          |
          |     1 arg too many
          |     ✗ NONE        ( 2 )      2
        _______________________________

Call arg type mismatch:
        _______________________________
          |
          |     'senpai.upTo()' called here
        7 |     b = a.upTo(2,2).len()~
          |           ^^^^
          |
          |     'senpai.upTo()' class method expects 1 argument
          |     EXPECTED     ACTUAL     ARG
          |     ✗ senpai     chan       2
          |
          |     1 arg too many
          |     ✗ NONE        ( 2 )      2
        _______________________________

Call arg type mismatch:
        _______________________________
          |
          |     'senpai.from()' called here
        8 |     b = a.from(2,2).len()~
          |           ^^^^
          |
          |     'senpai.from()' class method expects 1 argument
          |     EXPECTED     ACTUAL     ARG
          |     ✗ senpai     chan       2
          |
          |     1 arg too many
          |     ✗ NONE        ( 2 )      2
        _______________________________

Call arg type mismatch:
        ___________________________________
          |
          |     'senpai.substr()' called here
        9 |     b = a.substr(2,2,2).len()~
          |           ^^^^^^
          |
          |     'senpai.substr()' class method expects 2 arguments
          |     EXPECTED     ACTUAL     ARG
          |     ✓ chan       chan       2
          |     ✓ chan       chan       2
          |
          |     1 arg too many
          |     ✗ NONE        ( 2 )      2
        ___________________________________