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quartata
quartata
00:28
@Downgoat You currently use a recursive descent parser, right?
 
2 hours later…
Downgoat
Downgoat
02:21
@MᴀʀsUʟᴛᴏʀ thx
@quartata an LL parser, also a top-down parser
quartata
quartata
02:59
@Downgoat Have you considered the benefits of some form of bottom-up parser
 
1 hour later…
Downgoat
Downgoat
04:09
@quartata in the case of Cheddar a bottom-up parser wouldn't be as efficient
 
1 hour later…
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
05:16
@downgoat what's the difference?
Downgoat
Downgoat
@CᴏɴᴏʀO'Bʀɪᴇɴ bottom up parser works the opposite way. lemme make example:
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Ok
Downgoat
Downgoat
top down parser: I found expression! I found literal! I found number!
bottom up parser: I found number! I found literal! I found expression!
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Can I have an example example?
Downgoat
Downgoat
bottom up parsers are useful usually when you have prefixes with different suffixes. You can attempt different suffixes without reparsing the prefix
@CᴏɴᴏʀO'Bʀɪᴇɴ yes. lemme make it one sec
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
05:18
Ok
Downgoat
Downgoat 
       Expression
           +
   +---------------+
   +       +       +
literal   op     literal
  13       *        2
A top down parser would match an expression first, then a literla
You can think of it this way:
Top down parser would "attempt" to find a expression. If it finds an expression, it'll look for the first token of that expression (op or literal)
Bottom up parser would find a literal, then an op, than a literal and resolve it to an expressoin
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Huh
Downgoat
Downgoat
bottom up parsers have problems with ambiguity as you may be able to tell
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Yeah
Where did you learn all this?
Downgoat
Downgoat
idk.
i guess a lot of googling
i read like two pages on a book on compiler theory
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
05:26
Ooo which book
Downgoat
Downgoat
problem is stuff on internet like wikipedia described it in jargon no one understands
@CᴏɴᴏʀO'Bʀɪᴇɴ i have no idea rn, but i can find out if you'd like
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Please do :) in trying to write a compiler
*im
Downgoat
Downgoat
It's called "compilers" by alfred v. aho
amzn.com/0201100886
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Oh, cool! Thanks very much
Downgoat
Downgoat
np. it's old so you should be able to find a pdf somewhere :P
btw. TIL to use git rebase <branch> rather than git merge <branch>
git rebase is better when you want to merge two branches that have diverged because it'll put commits in the right order
@CᴏɴᴏʀO'Bʀɪᴇɴ can I delete string-stdlib since it's merge now?
Cᴏɴᴏʀ O'Bʀɪᴇɴ
Cᴏɴᴏʀ O'Bʀɪᴇɴ
05:48
Sure!
Also I am going to bed now. Night!
Downgoat
Downgoat
@CᴏɴᴏʀO'Bʀɪᴇɴ g'night!

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