mmbshmup/the_parser.p8

pico-8 cartridge // http://www.pico-8.com
version 41
__lua__
-- the parser

parser = {}
mknew(parser)

-- calls parse_into with a nop
-- emit function.
function parser:parse(str)
 self:parse_into(str, function() end)
end

-- read a file of commands and
-- execute them, emitting the
-- results from each call into
-- `emit` as a table per row.
--
-- a "command" is a method on
-- self. a row alternates
-- commands with args. when
-- calling a command, it also
-- gets a table of previous
-- results as the first arg.
-- args are split on ','.
function parser:parse_into(str, emit)
 for row in all(split(str, "\n")) do
  local prev = {}
  local sectors = split(row, ":")
  for i=1,#sectors,2 do
   local x = self[sectors[i]](self, prev, usplit(sectors[i+1]))
   if (x) add(prev, x)
  end
  emit(prev)
 end
end

-- saves prev[sel] as self.name.
-- if sel is unspecified, saves
-- all of prev (as a table).
function parser:saveas(prev, name, sel)
 self[name] = sel and prev[sel] or prev
end

-- returns its args, ignoring
-- prev. Used to stuff things
-- into prev. args are packed
-- if there's multiple.
function parser:val(_, ...)
 local ret := pack(...)
 if (#ret == 1) return ret[1]
 return ret
end

function parser:bind(_, fn, ...)
 local f = self[fn]
 return function()
  f(...)
 end
end