preprocessor
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- Subject: preprocessor
- From: Luiz Henrique de Figueiredo <lhf@...>
- Date: 2000年11月30日 01:17:12 -0200 (EDT)
Here is an implementation of the now defunct preprocessor.
As a bonus, '$if' and '$ifnot' now accept complete expressions instead
of just single variable names.
On the other hand, I think that errors in these expressions will abort the
whole preprocessing...
There's also an implementation of `dofile' that uses this preprocessor.
Enjoy.
--lhf
-- implementation of Lua 3.x preprocessor
function scan(in,out,name,ln,fp,pp,p)
local e=nil -- no `else' seen
p=pp and p -- ensure consistency of print flags
while 1 do
local s=read(in)
if s==nil then
if fp then return else error("unexpected end of file `"..name.."'") end
end
ln=ln+1
local i,j,c=strfind(s,"%$%s*(%w+)")
if not i then -- ordinary line
if not p then s="" end -- preserve line numbers
write(out,s,"\n")
else -- preprocessor line
write(out,"\n") -- preserve line numbers
local t=strsub(s,j+1,-1)
if c=="debug" then -- do nothing
elseif c=="nodebug" then -- do nothing
elseif c=="endinput" then return 0
elseif c=="if" then
local v=dostring("return "..t)
ln=scan(in,out,name,ln,nil,p,v)
if ln==0 then return 0 end
elseif c=="ifnot" then
local v=dostring("return "..t)
ln=scan(in,out,name,ln,nil,p,not v)
if ln==0 then return 0 end
elseif c=="end" then
if fp then
error("unmatched `endif' at line "..ln.." of file `"..name.."'")
else
return ln
end
elseif c=="else" then
if fp then
error("unmatched `else' at line "..ln.." of file `"..name.."'")
elseif e then
error("extraneous `else' at line "..ln.." of file `"..name.."'")
else
p=pp and not p -- invert print permission
e=1 -- `else' seen
end
else
error("unknown pragma `"..c.."' at line "..ln.." of file `"..name.."'")
end
end
end
end
function dofile(s)
local in,e=openfile(s,"r") assert(in,e)
local t=tmpname() assert(t)
local out,e=openfile(t,"w") assert(out,e)
scan(in,out,s,0,1,1,1)
closefile(out)
local a1,a2,a3,a4,a5,a6,a7,a8,a9=%dofile(t,s) -- lazy!
remove(t)
return a1,a2,a3,a4,a5,a6,a7,a8,a9
end