Module:Sandbox/Wnt/Expression

 --- this began long ago when a first test program for the Mandelbrot set went pear-shaped
 
 local p={}

 function chunk(text)
 local text=mw.ustring.gsub(text,"(%d%s*)E(%s*[%d%+%-])","%1 E %2") -- force space around E notation to avoid going nuts later
 local debuglog=""
 local chunks={type={}}
 local prowl=mw.ustring.gmatch(text,"(%S+)")
 local firstbit
 local num=1
 local op=2
 local var=3
 local warning=4
 local defs={num={"^([%d%.]*)(.*)$"},op={"^(E?)(.*)$","^([%(%)%*%+%-%?%%/!^]?)(.*)$"},var={"^(%a*)(.*)$"}}
 t=prowl()
 while t do
 local ot=t
 for i,j in pairs(defs) do
 for _,v in pairs(j) do
 firstbit,t=mw.ustring.match(t,v)
 debuglog=debuglog.."<"..tostring(firstbit)..","..tostring(t)..">"..tostring(i).."i"..tostring(j).."j"..tostring(t).."t"..tostring(v).."v"
 assert(t,debuglog) -- should always deliver a null string even if the target isn't there
 if firstbit ~= "" then
 table.insert(chunks,firstbit)
 table.insert(chunks.type,i)
 end
 end
 end
 if t==ot then
 firstbit,t=mw.ustring.match(t,"^(.)(.*)$")
 table.insert(chunks,'ignored:'..firstbit)
 table.insert(chunks.type,warning)
 end
 if t=="" then t=prowl() end -- if you run out of bits between spaces, pull a new interspace bit.
 end
 return chunks
 end

 function p.main(frame)
 local args=frame.args or {}
 local parent=frame.getParent(frame) or {}
 local pargs=parent.args or {}
 local expr=args.expr or pargs.expr or "" -- (Handle nothing in with nothing out?)
 local chunks=chunk(expr)
 return #chunks,"types"..table.concat(chunks.type,",").."values"..table.concat(chunks,",")
 -- check 1: getting the input sorted out into chunks
 end

 return p