On Wed, Mar 27, 2019 at 6:47 PM Soni "They/Them" L. <fakedme@gmail.com
<mailto:fakedme@gmail.com>> wrote:
I'm rolling with this weird idea. is it possible to make a simple
parser
out of tables? I tried some stuff but ran into a few issues. I don't
wanna use LPeg or anything more complicated than string.find(foo,
bar,
1, true).
e.g.:
local ltk = {} -- lua_tokens
ltk.string = {}
ltk['"'] = "string"
ltk["'"] = "string" -- how to handle end of string correctly?
ltk.string['\\'] = "escape"
ltk.string.escape = {}
ltk.string.escape['z'] = {}
ltk.string.escape['z'].next = ltk.string.escape['z']
for i, v in ipairs({" ", "\t", "\n", etc}) do
ltk.string.escape['z'][v] = "next"
end
ltk.string.escape['z'][''] = ltk.string -- not sure if there'd be a
better way to do this
-- etc
Not a bad start for someone who's never done this formally before.
There are a zillion different ways to define a parser. The Dragon Book
recommendation is well-given.
I think the insight you're missing is that the table really represents
the structure of a state machine. Your top-level table shouldn't
contain things like ["'"] = "string" directly; rather, you'd want
something like ltk.base["'"]. Then you wouldn't have
ltk.string.escape, you'd just have ltk.string and ltk.escape. The
nesting doesn't belong in the table itself; instead, your parser will
maintain a stack of states, and you push a state when you start into a
parsing rule and you pop it off when you've finished that rule.
