static boolean findFunctionInvocations_debug;

// these prefix tokens mark a non-invocation (TODO: expand)
static Set<S> findFunctionInvocations_pre = new HashSet(litlist(".", "void", "S", "String", "int", "bool", "boolean", "A", "Object", "O"));

static Set<String> findFunctionInvocations(L<S> tok, SS sf) {
  ret findFunctionInvocations(tok, sf, null);
}

// sf = set of functions to search for or null for any function
static Set<String> findFunctionInvocations(L<S> tok, SS sf, Collection<S> hardReferences) {
  ret findFunctionInvocations(tok, sf, hardReferences, null);
}

static Set<String> findFunctionInvocations(L<S> tok, SS sf, Collection<S> hardReferences, Set<S> haveFunctions) {
  int i;
  Set<String> l = new HashSet();
  while ((i = jfind(tok, "please include function *.")) >= 0) {
    String fname = tok.get(i+6);
    l.add(fname);
    hardReferences.add(fname);
    clearAllTokens(tok.subList(i, i+10));
  }

  boolean result = false;
  for (i = 1; i+2 < tok.size(); i += 2) {
    String f = tok.get(i);
    if (!isIdentifier(f)) continue;
    if (findFunctionInvocations_debug)
      System.out.println("Testing identifier " + f);
    if (!tok.get(i+2).equals("(")) continue;
    if (i == 1
        || !findFunctionInvocations_pre.contains(tok.get(i-2))
        || eq(get(tok, i-2), ".") && eq(get(tok, i-4), "main")) {
      boolean inSF = sf == null || sf.containsKey(f);
      if (findFunctionInvocations_debug)
        System.out.println("Possible invocation: " + f + ", inSF: " + inSF);
      if (inSF && !contains(haveFunctions, f) && l.add(f))
        print("Found standard function reference: " + lineAroundToken(tok, i));
    }
  }
  
  return l;
}