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Main program - town simulation exercise
this example from a Well House Consultants training course
Source code: town_simulation Module: U050
--[[
This program was set as an exersize by Graham Ellis on a Lua training course in Mexico (I run them worldwide - contact graham@wellho.net for details) Principles shown include the reading in of simulation / game elements from a data file (and cleaning that data) into several different types of 'object' (table in lua) so that the simulation can be run with different towns acting in a different manner, and yet with no horrid series of if ... elseif ... elseif ... else blocks - i.e. we're using polymorphism well. Error checking, version control, better comments, variable naming conventions all need further consideration, but this is just a demonstration! Sample data line from data file: Chippenham 28000 growth 4 150000 ]] -- town.lua contains the definition of all types of town -- (not like Java where it must be one class per file) require ("towns") fh,err = io.open("town_sim.txt") towns = {} -- Read the starting data into a table of towns while true do line = fh:read() if not line then break end -- Strip comments off the end of each line line = string.gsub(line,"#.*","") -- If there's anything left in the line ... if string.match(line,"%S") then -- this could usefully be a separate function. -- that function should probably be in a separate -- file for re-use later line = string.gsub(line,"^%s*","") place, pop, rss_type, tph, houseprice = string.match(line ,"(.-)\t+(.-)\t+(.-)\t+(.-)\t+(.*)") if rss_type == "growth" then current = growth.new(place,pop,tph, houseprice) elseif rss_type == "stable" then current = stable.new(place,pop,tph, houseprice) else -- DON'T throw away error lines - flag them! io.write ("Data error") current = nil end if current then towns[#towns+1] = current end end end --------- Data has been read in --------- Initialise tables for simulation results and --------- display initial data changes = {} prices = {} for _,v in pairs(towns) do print (" ",v) -- Save initial values as start or result sets changes[v.place] = {v.pop} prices[v.place] = {v.houseprice} end ---------- Run simulation -- 20 steps of 1 year for k = 1, 20 do -- print ("Running forward ".. k .. " years") totfact = 0 -- get factor total (for distribution of newcomers) for _,v in pairs(towns) do fftt = v:getfact() totfact = totfact + fftt end for _,v in pairs(towns) do fftt = v:getfact() incoming = v.pop -- Add newcomers in proportion to factor v:addpeeps(6000 * fftt / totfact) -- A certain percentage will move away v:wastage() outgoing = v.pop -- House prices change based on supply and demand v:change_house_prices(incoming, outgoing) -- Save the new values every fourth year if k % 4 == 0 then changes[v.place][#changes[v.place]+1] = v.pop prices[v.place][#prices[v.place]+1] = v.houseprice end end --[[ Commented out - dump the data annually for _,v in pairs(towns) do print (" ",v) end ]] end ----------- Display result tables io.write("\nProgression of population every 4 years\n") for k,v in pairs(changes) do io.write(string.format("%-15s",k)) for k9,v9 in pairs(v) do io.write(string.format("%6d",v9)) end io.write("\n") end io.write("\nProgression of house prices every 4 years\n") for k,v in pairs(prices) do io.write(string.format("%-15s",k)) for k9,v9 in pairs(v) do io.write(string.format("%7d",v9)) end io.write("\n") end Learn about this subject
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