Befunge

gistfile1.lua

local prg='0"!dlroW ,olleH">:#,_@'
local mem={}
local width=0
local sy=0
local stack={}
local function push(val)
	table.insert(stack,1,val%256)
end
local function pop(n)
	local v=stack[n or 1]
	table.remove(stack,n or 1)
	return v
end
for line in prg:gmatch("[^\n]+") do
	sy=sy+1
	width=math.max(width,#line)
	mem[sy]={string.byte(line,1,#line)}
end
for ly=1,sy do
	for lx=1,width do
		mem[ly][lx]=mem[ly][lx] or 32
	end
end
local x=1
local y=1
local dir=2
local dirs={
	["^"]=1,
	[">"]=2,
	["v"]=3,
	["<"]=4,
}
local strmode=false
while (mem[y] or {})[x] do
	local ins=string.char(mem[y][x])
	if strmode then
		if ins=="\"" then
			strmode=false
		else
			push(mem[y][x])
		end
	else
		if ins=="+" then
			push(pop()+pop())
		elseif ins=="-" then
			push(pop(2)-pop())
		elseif ins=="*" then
			push(pop(2)*pop())
		elseif ins=="/" then
			push(math.floor(pop(2)/pop()))
		elseif ins=="%" then
			push(pop(2)%pop())
		elseif ins=="!" then
			push(pop()==0 and 1 or 0)
		elseif ins=="`" then
			push(pop()>pop() and 1 or 0)
		elseif dirs[ins] then
			dir=dirs[ins]
		elseif ins=="?" then
			dir=math.random(1,4)
		elseif ins=="_" then
			dir=pop()==0 and 2 or 4
		elseif ins=="|" then
			dir=pop()==0 and 3 or 1
		elseif ins=="\"" then
			strmode=true
		elseif ins==":" then
			push(stack[1])
		elseif ins=="\\" then
			stack[1],stack[2]=stack[2],stack[1]
		elseif ins=="$" then
			pop()
		elseif ins=="." then
			io.write(pop())
		elseif ins=="," then
			io.write(string.char(pop()))
		elseif ins=="#" then
			x=x+(({[4]=-1,[2]=1})[dir] or 0)
			y=y+(({[1]=-1,[3]=1})[dir] or 0)
		elseif ins=="g" then
			push((mem[pop()] or {})[pop()] or 32)
		elseif ins=="p" then
			(mem[pop(2)] or {})[pop(2)]=pop()
		elseif ins=="&" then
			push(tonumber(io.read()))
		elseif ins=="~" then
			push(string.byte(io.read(1)))
		elseif ins=="@" then
			return
		elseif tonumber(ins) then
			push(tonumber(ins))
		end
	end
	x=x+(({[4]=-1,[2]=1})[dir] or 0)
	y=y+(({[1]=-1,[3]=1})[dir] or 0)
end