Re: Question about lstrip

[Luiz Henrique de Figueiredo <lhf@...>]

> I have a project that needs the same functionality as lstrip -d,
> except that the input and output need to be strings rather than a file
> and stdout respectively.

If you mean from within Lua, and not as a standalone application, then
the easiest way I think is to use a token filter in C that calls a Lua
callback with whatever representation of each token you need. See below
for an example.  

Build Lua with the patched llex.c and then run this test.lua:

     function INSPECTOR(line,token,value)
	     print("INSPECTOR",line,token,value)
     end
     assert(loadfile"test.lua")

To turn the INSPECTOR off, just set it to nil.
I hope it helps.
--lhf

/*
* proxy.c
* lexer proxy for Lua parser -- implements token inspection
* Luiz Henrique de Figueiredo <lhf@tecgraf.puc-rio.br>
* 12 Sep 2007 16:14:04
* This code is hereby placed in the public domain.
* Add <<#include "proxy.c">> just before the definition of luaX_next in llex.c
*/

#define INSPECTOR	"INSPECTOR"

static int nexttoken(LexState *ls, SemInfo *seminfo)
{
 lua_State *L=ls->L;
 lua_getglobal(L,INSPECTOR);
 if (lua_isnil(L,-1))
 {
  lua_pop(L,1);
  return llex(ls,seminfo);
 }
 else
 {
  for (;;)
  {
   int t=llex(ls,seminfo);
   lua_pushvalue(L,-1);
   lua_pushinteger(L,ls->linenumber);
   if (t<FIRST_RESERVED)
   {
    char s=t;
    lua_pushlstring(L,&s,1);
   }
   else
    lua_pushstring(L,luaX_tokens[t-FIRST_RESERVED]);
   if (t==TK_NAME || t==TK_STRING)
    lua_pushlstring(L,getstr(seminfo->ts),seminfo->ts->tsv.len);
   else if (t==TK_NUMBER)
    lua_pushnumber(L,seminfo->r);
   else
    lua_pushnil(L);
   lua_call(L,3,0);
   if (t==TK_EOS) break;
  }
  lua_pop(L,1);
  return TK_EOS;
 }
}

#define llex nexttoken