• Subject: Re: Lightweight syntax: a dissident view
• From: Luiz Henrique de Figueiredo <lhf@...>
• Date: Wed, 24 Nov 2010 17:23:45 -0200

```> Personally, I'd settle for a mature version of the token-filter patch
> being accepted. Then one can do just about anything (which is probably
> the most common criticism ;)) including \x(x+1).

To allow people to experiment with that syntax, here is an implementation
using a token filter written in C.

It converts
\x,y,z(x+(x-2)*g(x,y,z-2*(x+y))-y*z)
to
function(x,y,z) return x+(x-2)*g(x,y,z-2*(x+y))-y*z end

It works automatically for empty parameter lists:
\(x+z) --> function() return x+z end

--lhf

/*
* proxy.c
* lexer proxy for Lua parser -- implements '\x,y,z(exp)'
* Luiz Henrique de Figueiredo <lhf@tecgraf.puc-rio.br>
* 24 Nov 2010 17:17:44
* This code is hereby placed in the public domain.
* Add <<#include "proxy.c">> just before the definition of luaX_next in llex.c
*/

#include <string.h>

static int nexttoken(LexState *ls, SemInfo *seminfo)
{
static int state=0;
static int level=0;
int t;
switch (state)
{
case 0:
t=llex(ls,seminfo);
if (t=='\\') {
state=1;
t=TK_FUNCTION;
}
return t;
case 1:
state=2;
return '(';
case 2:
t=llex(ls,seminfo);
if (t=='(') {
level=1;
state=3;
t=')';
}
return t;
case 3:
state=4;
return TK_RETURN;
case 4:
t=llex(ls,seminfo);
if (t=='(') ++level;
else if (t==')') {
if (--level==0) {
state=0;
t=TK_END;
}
}
return t;
}
}

#define llex nexttoken

```