-- This file:
--   http://angg.twu.net/LUA/Stack1.lua.html
--   http://angg.twu.net/LUA/Stack1.lua
--           (find-angg "LUA/Stack1.lua")
-- Author: Eduardo Ochs <eduardoochs@gmail.com>
--
--  Used by: (find-angg "LUA/DiagForth1.lua")
--           (find-angggrep "grep --color=auto -nH --null -e Stack LUA/*.lua")
-- Based on: (find-dn6 "stacks.lua" "Stack")

-- «.Stack»		(to "Stack")
-- «.Stack-tests»	(to "Stack-tests")


-- «Stack»  (to ".Stack")
Stack = Class {
  type = "Stack",
  new  = function () return Stack {} end,
  __tostring = function (s) return s:tostring() end,
  __index = {
    tostring = function (s) return mapconcat(tostring, s, " ") end,
    print    = function (s) print(s); return s end,
    PP       = function (s) PP(s);    return s end,
    --
    push  = function (s,o) table.insert(s, o); return s end,
    pushs = function (s,...) for _,o in ipairs({...}) do s:push(o) end; return s end,
    --
    check     = function (s)   assert(#s>0, s.msg or "Empty stack"); return s end,
    drop      = function (s)   s:check(); s[#s]=nil; return s end,
    dropn     = function (s,n) for i=1,n  do s:drop() end; return s end,
    dropuntil = function (s,n) while #s>n do s:drop() end; return s end,
    clear     = function (s)   return s:dropn(#s) end,
    --
    dropn_ = function (s,n) s:dropn(n); return end,
    pop    = function (s) return                         s[#s], s:dropn_(1) end,
    pop2   = function (s) return                 s[#s-1],s[#s], s:dropn_(2) end,
    pop3   = function (s) return         s[#s-2],s[#s-1],s[#s], s:dropn_(3) end,
    pop4   = function (s) return s[#s-3],s[#s-2],s[#s-1],s[#s], s:dropn_(4) end,
    --
    pick = function (s,offset)   return s[#s-offset] end,
    pock = function (s,offset,o)        s[#s-offset] = o; return s end,
    --
    -- Methods for "metastacks", that are stacks whose elements
    -- are the depths of another stack, that is stored in `s.ds'.
    meta_push = function (ms) ms:push(#(ms.ds)); return ms end,
    meta_pop  = function (ms) ms.ds:dropuntil(ms:pop()); return ms end,
    meta_at   = function (ms,offset) return ds[ms:pick(0) + offset + 1] end,
  },
}

-- «Stack-tests»  (to ".Stack-tests")
--[[
* (eepitch-lua51)
* (eepitch-kill)
* (eepitch-lua51)
dofile "Stack1.lua"
ds = Stack.new()
= ds
= ds:push(22):push(33):pushs(44, 55, 66)  --> 22 33 44 55 66
= ds:pick(0)             -->         66
= ds:pick(1)             -->    55
= ds:pick(2)             --> 44

= ds:dropn(3):pushs(444,555,666)  --> 22 33 444 555 666
= ds:pop4()                       -->    33 444 555 666
= ds                              --> 22

ds     = Stack.new()
depths = Stack {ds=ds}
= ds:pushs(11, 22, 33, 44)  --> 11 22 33 44
= depths:meta_push()        -->             4
= ds:pushs(55, 66)          --> 11 22 33 44   55 66
= depths:meta_push()        -->             4       6
= ds:pushs(77, 88, 99)      --> 11 22 33 44   55 66   77 88 99
= depths:meta_at(0)         -->                       77
= depths:meta_at(1)         -->                          88
= depths:meta_at(2)         -->                             99
= depths                    -->             4       6
= ds                        --> 11 22 33 44   55 66   77 88 99
= depths:meta_pop()         -->             4
= ds                        --> 11 22 33 44   55 66
= depths:meta_pop()         -->            
= ds                        --> 11 22 33 44

= ds:clear()

--]]



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