Module:LogicUtils

Documentation for this module may be created at Module:LogicUtils/doc

local p = {}

function parse_io(kind, row, str)
	local count = tonumber(str)
	local names = {}

	if count == nil then
		-- str is a list of IO names
		names = mw.text.split(str, ",")
	else
		-- str is a number
		if count == 1 then
			names[1] = kind
		else
			for i=1,count do
				names[i] = string.format("%s %i", kind, i)
			end
		end
	end

	for i, v in ipairs(names) do
		row:tag('th')
			:wikitext(v)
	end

	return #names
end

local function eval(str, values)
    local stack = {}

    str:gsub("[^%s()]", function(c)
        if c == "&" or c == "|" or c == "^" then
            local v = table.remove(stack)
            if v == nil then error("Invalid expression: missing operand") end
            local v2 = table.remove(stack)
            if v2 == nil then error("Invalid expression: missing operand") end

            if c == "&" then
                table.insert(stack, v and v2)
            elseif c == "|" then
                table.insert(stack, v or v2)
            elseif c == "^" then
                table.insert(stack, v ~= v2)
            end
        elseif c == "!" then
            local v = table.remove(stack)
            if v == nil then error("Invalid expression: missing operand after '!'") end
            table.insert(stack, not v)
        else
            local index = string.find("abcdefghijklmnopqrstuvwxyz", c)
            if index then
                if values[index] == nil and not ignoreMissing then error("Value for variable '" .. c .. "' not provided") end

                table.insert(stack, values[index] or false)
            else
                error("Invalid character in expression: " .. c)
            end
        end
    end)

    return stack[1]
end

local function evalAll(str, num_vars, callback)
    local totalCombinations = 2 ^ num_vars
    local bit32 = require( 'bit32' )

    for i = 0, totalCombinations - 1 do
        local values = {}
        for j = 1, num_vars do
            values[j] = bit32.band(i, bit32.lshift(1, j - 1)) ~= 0
        end

        local result = eval(str, values)
        callback(values, result)
    end
end

local function renderCell(row, value)
    local style = "color:white; text-align:center;"
    if value == false then
        row:tag('td')
            :attr('style', 'background-color:#1f1e1e;'..style)
            :wikitext("0")
    elseif value == true then
        row:tag('td')
            :attr('style', 'background-color:#fd140f;'..style)
            :wikitext("1")
    else
        row:tag('td')
            :wikitext(value)
    end
end

p.truth_table = function(frame, args)
	local args = args or frame:getParent().args

    local tbl = mw.html.create('table')
        :addClass('wikitable')

	if args.caption ~= nil then
		tbl:tag('caption')
			:wikitext(args.caption)
	end

    local header = tbl:tag('tr')
	local nInputs = parse_io("Input", header, args.inputs)
	local nOutputs = parse_io("Output", header, args.outputs)

	local i = 1
	while args[i] ~= nil do
		local row = tbl:tag('tr')

		for token in string.gmatch(args[i], "[^%s]+") do
            renderCell(row, token == "1" and true or token == "0" and false or token)
		end

		i = i + 1
	end

    return tostring(tbl)
end

p.truth_table_auto = function(frame, args)
	local args = args or frame:getParent().args
	args.inputs = 2
	args.outputs = 1
	args.expr1 = "a b &"

    local tbl = mw.html.create('table')
        :addClass('wikitable')

	if args.caption ~= nil then
		tbl:tag('caption')
			:wikitext(args.caption)
	end

    local header = tbl:tag('tr')
	local nInputs = parse_io("Input", header, args.inputs)
	local nOutputs = parse_io("Output", header, args.outputs)

	for i = 1,nOutputs do
		local row = tbl:tag('tr')
        local expr = args["expr"..i]
        if expr == nil then
            error("Missing expression for output " .. i)
        end

        evalAll(expr, nInputs, function(values, result)
            for j = 1,nInputs do
                renderCell(row, values[j])
            end
            renderCell(row, result)
        end)

		i = i + 1
	end

    return tostring(tbl)
end

return p