Show EU power values more readable (#424)

Add the EU_string helper function
In comparison to pretty_num it uses SI prefixes, adds "EU" (e.g. kEU) and rounds the number for readability
Add a constant_digit_count boolean setting

technic/doc/api.md

@@ -11,9 +11,12 @@ switching station handles the network activity.
 
 Helper functions
 ----------------
+* `technic.EU_string(num)`
+	* Converts num to a human-readable string (see pretty_num)
+	  and adds the `EU` unit
+	* Use this function when showing players energy values
 * `technic.pretty_num(num)`
-	* Converts the number `num` to a human-readable string.
+	* Converts the number `num` to a human-readable string with SI prefixes
-	* Use this function when showing players power values.
 * `technic.swap_node(pos, nodename)`
 	* Same as `mintest.swap_node` but it only changes the nodename.
 	* It uses `minetest.get_node` before swapping to ensure the new nodename

technic/helpers.lua

@@ -1,23 +1,56 @@
-local digit_sep_esc
+local constant_digit_count = technic.config:get("constant_digit_count")
-do
-	local sep = technic.config:get("digit_separator")
-	sep = tonumber(sep) and string.char(sep) or sep or " "
-	-- Escape for gsub
-	for magic in ("().%+-*?[^$"):gmatch(".") do
-		if sep == magic then
-			sep = "%"..sep
-		end
-	end
-	digit_sep_esc = sep
-end
-
 
+-- converts a number to a readable string with SI prefix, e.g. 10000 → "10 k",
+-- 15 → "15 ", 0.1501 → "150.1 m"
+-- a non-breaking space (U+a0) instead of a usual one is put after number
+-- The precision is 4 digits
+local prefixes = {[-8] = "y", [-7] = "z", [-6] = "a", [-5] = "f", [-4] = "p",
+	[-3] = "n", [-2] = "µ", [-1] = "m", [0] = "",  [1] = "k", [2] = "M",
+	[3] = "G", [4] = "T", [5] = "P", [6] = "E", [7] = "Z", [8] = "Y"}
 function technic.pretty_num(num)
-	local str, k = tostring(num), nil
+	-- the small number added is due to floating point inaccuracy
-	repeat
+	local b = math.floor(math.log10(math.abs(num)) +0.000001)
-		str, k = str:gsub("^(-?%d+)(%d%d%d)", "%1"..digit_sep_esc.."%2")
+	local pref_i
-	until k == 0
+	if b ~= 0 then
-	return str
+		-- b is decremented by 1 to avoid a single digit with many decimals,
+		-- e.g. instead of 1.021 MEU, 1021 kEU is shown
+		pref_i = math.floor((b - 1) / 3)
+	else
+		-- as special case, avoid showing e.g. 1100 mEU instead of 1.1 EU
+		pref_i = 0
+	end
+	if not prefixes[pref_i] then
+		-- This happens for 0, nan, inf, very big values, etc.
+		if num == 0 then
+			-- handle 0 explicilty to avoid showing "-0"
+			if not constant_digit_count then
+				return "0 "
+			end
+			-- gives 0.000
+			return string.format("%.3f ", 0)
+		end
+		return string.format("%.4g ", num)
+	end
+
+	num = num * 10 ^ (-3 * pref_i)
+	if constant_digit_count then
+		local comma_digits_cnt = 3 - (b - 3 * pref_i)
+		return string.format("%." .. comma_digits_cnt .. "f %s",
+			num, prefixes[pref_i])
+	end
+	return string.format("%.4g %s", num, prefixes[pref_i])
+end
+
+-- some unittests
+assert(technic.pretty_num(-0) == "0 ")
+assert(technic.pretty_num(0) == "0 ")
+assert(technic.pretty_num(1234) == "1234 ")
+assert(technic.pretty_num(123456789) == "123.5 M")
+
+
+-- used to display power values
+function technic.EU_string(num)
+	return technic.pretty_num(num) .. "EU"
 end
 
 

technic/machines/LV/solar_panel.lua

@@ -35,7 +35,8 @@ local run = function(pos, node)
 		local charge_to_give = math.floor((light + pos1.y) * 3)
 		charge_to_give = math.max(charge_to_give, 0)
 		charge_to_give = math.min(charge_to_give, 200)
-		meta:set_string("infotext", S("@1 Active (@2 EU)", machine_name, technic.pretty_num(charge_to_give)))
+		meta:set_string("infotext", S("@1 Active (@2)", machine_name,
+			technic.EU_string(charge_to_give)))
 		meta:set_int("LV_EU_supply", charge_to_give)
 	else
 		meta:set_string("infotext", S("%s Idle"):format(machine_name))

technic/machines/MV/wind_mill.lua

@@ -60,7 +60,8 @@ local run = function(pos, node)
 	elseif check == true then
 		local power = math.min(pos.y * 100, 5000)
 		meta:set_int("MV_EU_supply", power)
-		meta:set_string("infotext", S("@1 (@2 EU)", machine_name, technic.pretty_num(power)))
+		meta:set_string("infotext", S("@1 (@2)", machine_name,
+			technic.EU_string(power)))
 	end
 	-- check == nil: assume nothing has changed
 end

technic/machines/power_monitor.lua

@@ -55,7 +55,7 @@ minetest.register_abm({
 			local demand = sw_meta:get_int("demand")
 			meta:set_string("infotext",
 					S("Power Monitor. Supply: @1 Demand: @2",
-					technic.pretty_num(supply), technic.pretty_num(demand)))
+					technic.EU_string(supply), technic.EU_string(demand)))
 		else
 			meta:set_string("infotext",S("Power Monitor Has No Network"))
 		end

technic/machines/register/battery_box.lua

@@ -256,7 +256,8 @@ function technic.register_battery_box(data)
 		local charge_percent = math.floor(current_charge / max_charge * 100)
 		meta:set_string("formspec", formspec..add_on_off_buttons(meta, ltier, charge_percent))
 		local infotext = S("@1 Battery Box: @2 / @3", tier,
-				technic.pretty_num(current_charge), technic.pretty_num(max_charge))
+				technic.EU_string(current_charge),
+				technic.EU_string(max_charge))
 		if eu_input == 0 then
 			infotext = S("%s Idle"):format(infotext)
 		end

technic/machines/register/solar_array.lua

@@ -30,7 +30,8 @@ function technic.register_solar_array(data)
 			local charge_to_give = math.floor((light + pos.y) * data.power)
 			charge_to_give = math.max(charge_to_give, 0)
 			charge_to_give = math.min(charge_to_give, data.power * 50)
-			meta:set_string("infotext", S("@1 Active (@2 EU)", machine_name, technic.pretty_num(charge_to_give)))
+			meta:set_string("infotext", S("@1 Active (@2)", machine_name,
+				technic.EU_string(charge_to_give)))
 			meta:set_int(tier.."_EU_supply", charge_to_give)
 		else
 			meta:set_string("infotext", S("%s Idle"):format(machine_name))

technic/machines/supply_converter.lua

@@ -149,7 +149,9 @@ local run = function(pos, node, run_stage)
 		meta:set_int(from.."_EU_supply", 0)
 		meta:set_int(to.."_EU_demand", 0)
 		meta:set_int(to.."_EU_supply", input * remain)
-		meta:set_string("infotext", S("@1 (@2 @3 -> @4 @5)", machine_name, technic.pretty_num(input), from, technic.pretty_num(input * remain), to))
+		meta:set_string("infotext", S("@1 (@2 @3 -> @4 @5)", machine_name,
+			technic.EU_string(input), from,
+			technic.EU_string(input * remain), to))
 	else
 		meta:set_string("infotext", S("%s Has Bad Cabling"):format(machine_name))
 		if to then

technic/machines/switching_station.lua

@@ -361,9 +361,9 @@ minetest.register_abm({
 		end
 		--dprint("Total BA demand:"..BA_eu_demand)
 
-		meta:set_string("infotext",
+		meta:set_string("infotext", S("@1. Supply: @2 Demand: @3",
-				S("@1. Supply: @2 Demand: @3",
+				machine_name, technic.EU_string(PR_eu_supply),
-				machine_name, technic.pretty_num(PR_eu_supply), technic.pretty_num(RE_eu_demand)))
+				technic.EU_string(RE_eu_demand)))
 
 		-- If mesecon signal and power supply or demand changed then
 		-- send them via digilines.