sbool ctxExpandMacros_debug;

static S ctxExpandMacros(S s, SS macros) {
  while true {
    S s2 = ctxExpandMacros_step(s, macros);
    if (eq(s, s2)) ret s;
    s = s2;
  }
}

static S ctxExpandMacros_step(S s, SS macros) {
  Matcher m = regexp("#([A-Z_0-9]+)#", s);
  while (m.find()) {
    if (ctxExpandMacros_debug)
      print("Replacing " + m.group(1));
    S key = m.group(1);
    S macro = macros.get(key);
    if (macro == null) macro = "#\\\"\\+\\?@";
    s = s.replace(m.group(), macro);
  }
  ret s;
}