-- This file:
--   http://anggtwu.net/LUA/Pratt2.lua.html
--   http://anggtwu.net/LUA/Pratt2.lua
--          (find-angg "LUA/Pratt2.lua")
-- Author: Eduardo Ochs <eduardoochs@gmail.com>
--
-- (defun p2 () (interactive) (find-angg "LUA/Pratt2.lua"))
-- (defun e1 () (interactive) (find-angg "LUA/ELpeg1.lua"))
-- (find-angg "LUA/ELpeg1.lua")
-- (find-angg "LUA/Tree1.lua")
-- (find-es "pratt")

require "ELpeg1"      -- (find-angg "LUA/ELpeg1.lua")

ptable = VTable {
  ["num"] = HTable {lbp="err", rbp="err"},
  ["end"] = HTable {lbp=0,     rbp="err"},
  ["+"]   = HTable {lbp=10,    rbp=10},
  ["*"]   = HTable {lbp=20,    rbp=20},
  ["^"]   = HTable {lbp=30,    rbp=30},
}

mkbin  = function (a, op, b) return AST {[0]=op, a, b} end

GetTokens = Class {
  type    = "GetTokens",
  from    = function (str)
      local isnum = function (s) return s:match("^[0-9]+$") end
      local f     = function (s) return isnum(s) and s+0 or s end
      return GetTokens {pos=1, unpack(map(f, split(str)))}
    end,
  __tostring = function (gt)
      local f = function (i) return format("  %d:%s", i, mytostring(gt[i])) end
      return format("pos=%d %s", gt.pos, mapconcat(f, seq(1,#gt)))
    end,
  __index = {
    raw  = function (gt) return gt[gt.pos] end,
    here = function (gt) return type(gt:raw())=="number" and "num" or gt:raw() end,
    pt   = function (gt) return ptable[gt:here()] end,
    lbp  = function (gt) return gt:pt().lbp end,
    --
    accept_1    = function (gt) local tk=gt:raw(); gt.pos=gt.pos+1; return tk end,
    accept_opb  = function (gt,rbp) return gt:accept_1(), gt:accept_b(rbp) end,
    accept_b    = function (gt,rbp) return gt:accept_1() end,    -- stub
    accept_a    = function (gt,rbp) return gt:add_opbs(rbp, gt:accept_1()) end,
    --
    add_opb  = function (gt,rbp,a)
        local op,b = gt:accept_opb(rbp)
        return mkbin(a,op,b)
      end,
    add_opbs = function (gt,rbp,a)
        while gt:lbp() > rbp do
          a = gt:add_opb(rbp,a)
        end
        return a
      end,
  },
}



--[[
* (eepitch-lua51)
* (eepitch-kill)
* (eepitch-lua51)
dofile "Pratt2.lua"

= ptable
tks = GetTokens.from(" 2 * 3 + 4 ^ 5 end ")
= tks
= tks:raw()
= tks:here()
= tks:pt()
tks.pos = tks.pos + 1
= tks:raw()

tks = GetTokens.from(" 200 * 300 + 400 ^ 500 end ")
= tks:accept_a()

a0 = tks:accept_1()
a0 = tks:add_opbs(0, a0)
= a0

= a0
= tks
= tks:lbp()
a0 = tks:add_opb(0, a0)
= tks
= tks:lbp()
a0 = tks:add_opb(0, a0)
= tks:lbp()
a0 = tks:add_opb(0, a0)
= tks:lbp()
a0 = tks:add_opbs(0, a0)
= a0



--]]



-- Local Variables:
-- coding:  utf-8-unix
-- End: