A concatenative programming language inspired by FORTH and implemented in Lua.

5-3.lua

pc=1			--program counter
program = {}		--array of words in program
dict = {}	--dictionary of user defined words
prim = {}	--language keywords
stack= {}	--working stack
rstack = {} --2nd stack
mem = {}		--memory
mode = "interpret"
alive = true		--used for halting and error
c_word = ""

function push(n)
	stack[#stack+1]=n 
end

function pop()
	if #stack > 0 then
		temp = stack[#stack]
		stack[#stack]=nil
	else
		io.write("Stack Underflow")
		temp = 0
	end
	return temp
end

prim["+"] = function() push(pop()+pop()) end
prim["*"] = function() push(pop()*pop()) end
prim["-"] = function() local a = pop(); push(pop()-a) end
prim["/"] = function() local a = pop(); push(pop()/a) end
prim["."] = function() io.write(pop()) end
prim["@"] = function() local addr = pop(); local data = mem[addr] or 0; push(data) end
prim["!"] = function() local addr = pop(); mem[addr] = pop() end
prim.BL = function() io.write(" ") end
prim.EMIT = function() io.write(string.char(pop())) end

prim.FUNC = function() mode = "pre-compile" end

eval = function(s)
		if prim[s] then	--if word is a language primitive
			prim[s]()				--execute it
		elseif dict[s] then	--if word is a user defined function
			for i = 1,#dict[s] do	--step through each word in definition
				process(dict[s][i])		--and process it
			end
		elseif type(tonumber(s)) == 'number' then	--if word is a number
			push(tonumber(s))	--push it on the stack
		else		--otherwise report the error
			io.write("\nError: ",s)
			alive=false
		end
end

process = function(s)	--process by mode and update modes
	if mode == "interpret" then
		eval(s)
	elseif mode == "pre-compile" then
		dict[s]={}
		c_word = s
		mode = "compile"
	elseif mode == "compile" then
		if s ~= "ENDFUNC" then
			dict[c_word][#dict[c_word]+1] = s
		else
			mode = "interpret"
		end
	end
end

-- ******* MAIN LOOP ********
io.write('>')		--display our prompt
for line in io.lines(arg[1]) do		--grab each line of std input
	program=nil;program={}
	for word in string.gmatch(line, '([^%s]+)') do --separate each whitespace delimited word
		program[#program+1] = string.upper(word)	--and put word into program array
	end
	pc=0;alive=true
	while alive==true do
		pc=pc+1
		if pc > #program then
			alive = false
		else
			process(program[pc])
		end
	end
	io.write('\n>')		--display our prompt before looping back for more input
end

readme.md

#5 A stack-based concatenative forthlike system. Not intended as a toy, but probableeee a damn toy.

##Example Code FUNC star 42 EMIT ENDFUNC star Output: *