在Arrays C中保存函数

我有一个新问题，我正在使用一个名为interpreter的类：

Interpreter.h

#ifndef INTERPRETER_H_
#define INTERPRETER_H_

#include <string>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>

using namespace std;

class Interpreter {
public:
   static Interpreter* getInstance();
   typedef void (*fn)(int, int, int, int);
   static fn opcodes[44];
   static fn functions[43];
private:
   Interpreter() {
      opcodes[9] = addiu;
      opcodes[3] = jal;
      opcodes[8] = addi;
      opcodes[4] = beq;
      opcodes[43] = sw;

      functions[32] = add;
      functions[33] = addu;
      functions[34] = sub;
      functions[18] = mflo;
      functions[26] = div;
      functions[12] = syscall;
      functions[8] = jr;

}
;
void addiu(int, int, int, int);
void addi(int, int, int, int);
void jal(int, int, int, int);
void beq(int, int, int, int);
void sw(int, int, int, int);

void add(int, int, int, int);
void addu(int, int, int, int);
void sub(int, int, int, int);
void mflo(int, int, int, int);
void div(int, int, int, int);
void syscall(int, int, int, int);
void jr(int, int, int, int);


static Interpreter* _instance;
};

 #endif /* INTERPRETER_H_ */

Interpreter.cpp

#include "Interpreter.h"

Interpreter* Interpreter::_instance = NULL;

Interpreter* Interpreter::getInstance() {
if (_instance == NULL) {
    _instance = new Interpreter();
}
return _instance;
}



 void Interpreter::addiu(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::addi(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::jal(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::beq(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::sw(int rs, int rt, int rd, int shamt) {

 }



 void Interpreter::add(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::addu(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::sub(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::mflo(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::div(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::syscall(int rs, int rt, int rd, int shamt) {

 }

 void Interpreter::jr(int rs, int rt, int rd, int shamt) {

 }

但是当我尝试将函数保存在数组操作码或函数中时，程序在.h文件中有错误，完全在私有构造函数Interpreter（）中 .

错误是：

不能将'Interpreter :: addiu'从类型'void（Interpreter ::）（int，int，int，int）'转换为'Interpreter :: fn {aka void（*）（int，int，int，int）} “

谢谢你的帮助