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luaforth

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A simplistic and decently fast base implementation of a Forth parser.

If you expect a fully featured forth here, you're wrong.

This is made for people who want to embed a Forth-like into their project.

Usage

  1. require/load luaforth.

  2. Create an environment.

  3. Call new_stack, new_environment = luaforth.eval(program_source, environment[, stack, program_source_start_position]).

Tada!

Example

See luaforth.simple_env here or below.

-- Example env that has %L to evaluate the line and [L L] pairs to evaluate a small block of Lua code.
local simple_env = {
	["%L"] = {
		_fn=function(stack, env, str)
			local f, err = loadstring("return " .. str)
			if err then
				f, err = loadstring(str)
				if err then
					error(err, 0)
				end
			end
			return f()
		end,
		_parse = "line"
	},
	["[L"] = {
		_fn=function(stack, env, str)
			local f, err = loadstring("return " .. str)
			if err then
				f, err = loadstring(str)
				if err then
					error(err, 0)
				end
			end
			return f()
		end,
		_parse = "endsign",
		_endsign = "L]"
	}
}

-- Function creation.
luaforth.simple_env[":"] = {
	_fn = function(stack, env, fn)
		local nme, prg = string.match(fn, "^(.-) (.-)$")
		luaforth.simple_env[nme] = {
			_fn = function(stack, env)
				return luaforth.eval(prg, env, stack)
			end,
			_fnret = "newstack"
		}
	end,
	_parse = "endsign",
	_endsign = ";"
}

Environment

Contains words, strings, booleans, numbers and other things that the forth instance will be able to use.

Word Structure

Words are Forth jargon for functions.

Look here or below to see how they are structured in this implementation.

-- Word structure:
-- env[name] = {
--  _fn = func -- function that runs the logic
--  _fnret = ["pushtostack", "newstack"] -- wether the function's return values should be added to the stack or _be_ the stack. Defaults to pushtostack.
--  _args = n -- number of arguments which are pop'd from the stack, defaults to 0
--  _parse = ["line"|"word"|"endsign"|"pattern"] -- optional advanced parsing, line passes the whole line to the word, word only the next word, pattern parses given pattern, endsign until...
--  _endsign = string -- the given endsign appears.
--  _pattern = pattern -- pattern for parse option
-- }

License

MIT

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A simple Forth in Lua for embedded usage.

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