Simple though this is, it is surprisingly powerful. A slightly more complex version, with a couple of extra features, can be found at the SlightlyLessSimpleLuaPreprocessor.

function prep(file)
 local chunk = {n=0}
 for line in file:lines() do
 if string.find(line, "^#") then
 table.insert(chunk, string.sub(line, 2) .. "\n")
 else
 local last = 1
 for text, expr, index in string.gmatch(line, "(.-)$(%b())()") do 
 last = index
 if text ~= "" then
 table.insert(chunk, string.format('io.write %q ', text))
 end
 table.insert(chunk, string.format('io.write%s ', expr))
 end
 table.insert(chunk, string.format('io.write %q\n',
 string.sub(line, last).."\n"))
 end
 end
 return loadstring(table.concat(chunk))()
end

Lines starting with # are executed as Lua. Other lines are sent through as is, except that $(...) appearing anywhere in them is executed. (No parsing is done, so you have to be careful with your $('s)

Sample input:

#if DEBUG then
 function log(fmt, ...) print(string.format(fmt, unpack(arg))) end
#else
 function log() end
#end
#for i = 0, 10 do
 var$(i) = $(math.sin(math.pi * i / 10))
#end

Sample output:

> prep(assert(io.open"sample.luap"))
 function log() end
 var0 = 0
 var1 = 0.30901699437495
 var2 = 0.58778525229247
 var3 = 0.80901699437495
 var4 = 0.95105651629515
 var5 = 1
 var6 = 0.95105651629515
 var7 = 0.80901699437495
 var8 = 0.58778525229247
 var9 = 0.30901699437495
 var10 = 1.2246467991474e-16
> DEBUG = true
> prep(assert(io.open"sample.luap"))
 function log(fmt, ...) print(string.format(fmt, unpack(arg))) end
 var0 = 0
 var1 = 0.30901699437495
 var2 = 0.58778525229247
 var3 = 0.80901699437495
 var4 = 0.95105651629515
 var5 = 1
 var6 = 0.95105651629515
 var7 = 0.80901699437495
 var8 = 0.58778525229247
 var9 = 0.30901699437495
 var10 = 1.2246467991474e-16

---

RecentChanges · preferences
edit · history
Last edited July 3, 2013 2:02 pm GMT (diff)