Inline Variables In String

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Inline variables inside strings

One of the features I loved in Ruby and PHP was the ability to include variables inside strings, example print "Hello ${Name}" The following patch does the same thing but only for the doc string type, strings starting with [[ and ending with ]]. It uses the "|" character to represent the open and close braces.

To add variables inline example :

output = [[Hello |name|, welcome to |get_company_name()|. ]]

What the patch does is quite literally convert the above to:

output = [[Hello ]]..name..[[, welcome to ]]..get_company_name()..[[. ]]

--Sam Lie

Important Note: Somehow, I needed another character as a means to represent the closing brace inside the code, and I have arbitarily chosen '¶' , what this means if somehow you have that character in your string (specially when you are using foreign language encoding) you will get a syntax error. I don't know if there is the solution to this problem as yet.

int luaX_lex (LexState *LS, SemInfo *seminfo) {
  for (;;) {
    switch (LS->current) {

      case '\n': {
        inclinenumber(LS);
        continue;
      }
      case '-': {
        next(LS);
        if (LS->current != '-') return '-';
        /* else is a comment */
        next(LS);
        if (LS->current == '[' && (next(LS), LS->current == '['))
          read_long_string(LS, NULL);  /* long comment */
        else  /* short comment */
          while (LS->current != '\n' && LS->current != EOZ)
            next(LS);
        continue;
      }
      case '[': {
        next(LS);
        if (LS->current != '[') return '[';
        else {
          read_long_string(LS, seminfo);
          return TK_STRING;
        }
      }
      case '=': {
        next(LS);
        if (LS->current != '=') return '=';
        else { next(LS); return TK_EQ; }
      }
      case '<': {
        next(LS);
        if (LS->current != '=') return '<';
        else { next(LS); return TK_LE; }
      }
      case '>': {
        next(LS);
        if (LS->current != '=') return '>';
        else { next(LS); return TK_GE; }
      }
      case '~': {
        next(LS);
        if (LS->current != '=') return '~';
        else { next(LS); return TK_NE; }
      }
      case '"':
      case '\'': {
        read_string(LS, LS->current, seminfo);
        return TK_STRING;
      }

	// added!!!
        //------------------------------
      case '|': {
	 LS->current = '¶';
	 return TK_CONCAT;
      }

      case '¶': {
	read_long_string(LS, seminfo);
	return TK_STRING;
	}
        //------------------------------

      case '.': {
        next(LS);
        if (LS->current == '.') {
          next(LS);
          if (LS->current == '.') {
            next(LS);
            return TK_DOTS;   /* ... */
          }
          else return TK_CONCAT;   /* .. */
        }

        else if (!isdigit(LS->current)) return '.';
        else {
          read_numeral(LS, 1, seminfo);
          return TK_NUMBER;
        }
      }
      case EOZ: {
        return TK_EOS;
      }
      default: {
        if (isspace(LS->current)) {
          next(LS);
          continue;
        }
        else if (isdigit(LS->current)) {
          read_numeral(LS, 0, seminfo);
          return TK_NUMBER;
        }
        else if (isalpha(LS->current) || LS->current == '_') {
          /* identifier or reserved word */
          size_t l = readname(LS);
          TString *ts = luaS_newlstr(LS->L, luaZ_buffer(LS->buff), l);
          if (ts->tsv.reserved > 0)  /* reserved word? */
            return ts->tsv.reserved - 1 + FIRST_RESERVED;
          seminfo->ts = ts;
          return TK_NAME;
        }
        else {
          int c = LS->current;
          if (iscntrl(c))
            luaX_error(LS, "invalid control char",
                           luaO_pushfstring(LS->L, "char(%d)", c));
          next(LS);
          return c;  /* single-char tokens (+ - / ...) */
        }
      }
    }
  }
}


static void read_long_string (LexState *LS, SemInfo *seminfo) {
  int cont = 0;
  size_t l = 0;
  checkbuffer(LS, l);
  save(LS, '[', l);  /* save first `[' */
  save_and_next(LS, l);  /* pass the second `[' */
  if (LS->current == '\n')  /* string starts with a newline? */
    inclinenumber(LS);  /* skip it */
  for (;;) {
    checkbuffer(LS, l);
    switch (LS->current) {
      case EOZ:
        save(LS, '\0', l);
        luaX_lexerror(LS, (seminfo) ? "unfinished long string" :
                                   "unfinished long comment", TK_EOS);
        break;  /* to avoid warnings */
      case '[':
        save_and_next(LS, l);
        if (LS->current == '[') {
          cont++;
          save_and_next(LS, l);
        }
        continue;
      case ']':
        save_and_next(LS, l);
        if (LS->current == ']') {
          if (cont == 0) goto endloop;
          cont--;
          save_and_next(LS, l);
        }
        continue;

// added
//------------------------------
      case '|':
		save(LS, ']', l);  

		LS->lookahead.token = TK_CONCAT;
        goto endloop;
        continue;
//------------------------------

      case '\n':
        save(LS, '\n', l);
        inclinenumber(LS);
        if (!seminfo) l = 0;  /* reset buffer to avoid wasting space */
        continue;
      default:
        save_and_next(LS, l);
    }
  } endloop:
  save_and_next(LS, l);  /* skip the second `]' */
  save(LS, '\0', l);
  if (seminfo)
    seminfo->ts = luaS_newlstr(LS->L, luaZ_buffer(LS->buff) + 2, l - 5);
}