svoid tok_replaceColonEqualsSyntax(LS tok) {

  int i;

  // "field := value" for defining fields e.g. in "uniq"

  while ((i = jfind_check(":", tok, "<id> :=")) >= 0) {

    S id = tok.get(i);

    // special case for null := which we interpret as actually null,

    // not "null"

    S string = eq(id, "null") ? id : quote(id);

    tok.set(i, string);

    tok.set(i+2, ",");

    tok.set(i+4, "");

    reTok(tok, i, i+5);

  }

  // "quoted" := value

  while ((i = jfind_check(":", tok, "<quoted> :=")) >= 0) {

    tok.set(i+2, ",");

    tok.set(i+4, "");

    reTok(tok, i, i+5);

  }

  // <int> := value

  while ((i = jfind_check(":", tok, "<int> :=")) >= 0) {

    tok.set(i+2, ",");

    tok.set(i+4, "");

    reTok(tok, i, i+5);

  }

  // all other cases: just replace with comma

  jreplace(tok, ":=", ",");

}