主要原因是我使用了函数指针，而函数指针所指函数须得是静态才行

错误代码：

class Solution {public:string ReverseSentence(string str) {typedef string::const_iterator const_iter;const_iter b = str.begin();const_iter e = str.end();string ret;int first = 1;while( b != e ){b = find_if( b, e, legal );if( b < e ){const_iter after = find_if( b, e, illegal ); // 这里的调用出了问题，编译出错reference to non-static member function must be calledif( ret != "" ) ret = string(b, after) + " " + ret;else ret = string(b, after) + ret;b = after;}else{if( 1 == first ) return str;else first = 2;}}return ret;}
private:bool legal( char ch ){ return !illegal(ch); } // 这里是问题bool illegal( char ch ){ return isspace(ch); }
};

解决

分析上面的错误，应该说的是，find_if的第三个参数应该调用一个non static函数，这是什么原因？我们来看下find_if的代码

template<class InputIterator, class UnaryPredicate>InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred)
{while (first!=last) {if (pred(*first)) return first;++first;}return last;
}

第三个谓词pred是一个非成员函数，因为pred的调用过程只有一个参数，就是*first。但是，对于像bool legal(char ch)这样的成员函数，它是属于类的，所以调用它必须需要对象才可以，这是因为bool legal这样的函数完整的标签是：

bool legal( Solution* this, char ch );

也就是它有一个implicit parameter，这才导致它无法被find_if这样的函数调用，主要是参数不匹配。当然，把这个函数改成static即可。

如果一定要非静态引用怎么办？

#include <string>
#include <memory>
#include "mutex"#ifndef HV_THREAD_POOL_H_
#define HV_THREAD_POOL_H_#include <vector>
#include <thread>
#include <queue>
#include <functional>
#include <atomic>
#include <mutex>
#include <condition_variable>
#include <future>
#include <memory>
#include <utility>
#include <stack>class HThreadPool {public:using Task = std::function<void()>;HThreadPool(int size = std::thread::hardware_concurrency()): pool_size(size), idle_num(size), status(STOP) {}~HThreadPool() {stop();}int start() {if (status == STOP) {status = RUNNING;for (int i = 0; i < pool_size; ++i) {workers.emplace_back(std::thread([this]{while (status != STOP) {while (status == PAUSE) {std::this_thread::yield();}Task task;{std::unique_lock<std::mutex> locker(_mutex);_cond.wait(locker, [this]{return status == STOP || !tasks.empty();});if (status == STOP) return;if (!tasks.empty()) {--idle_num;task = std::move(tasks.top());tasks.pop();}}task();++idle_num;}}));}}return 0;}int clear() {std::unique_lock<std::mutex> locker(_mutex);if (!tasks.empty()) {std::stack<Task>().swap(tasks);}return 0;}int stop() {if (status != STOP) {status = STOP;_cond.notify_all();for (auto& worker : workers) {worker.join();}}return 0;}int pause() {if (status == RUNNING) {status = PAUSE;}return 0;}int resume() {if (status == PAUSE) {status = RUNNING;}return 0;}int wait() {while (1) {if (status == STOP || (tasks.empty() && idle_num == pool_size)) {break;}std::this_thread::yield();}return 0;}// return a future, calling future.get() will wait task done and return RetType.// commit(fn, args...)// commit(std::bind(&Class::mem_fn, &obj))// commit(std::mem_fn(&Class::mem_fn, &obj))template<class Fn, class... Args>auto commit(Fn&& fn, Args&&... args) -> std::future<decltype(fn(args...))> {using RetType = decltype(fn(args...));auto task = std::make_shared<std::packaged_task<RetType()> >(std::bind(std::forward<Fn>(fn), std::forward<Args>(args)...));std::future<RetType> future = task->get_future();{std::lock_guard<std::mutex> locker(_mutex);tasks.emplace([task]{(*task)();});}_cond.notify_one();return future;}public:enum Status {STOP,RUNNING,PAUSE,};int                 pool_size;std::atomic<int>    idle_num;std::atomic<Status> status;std::vector<std::thread>    workers;std::stack<Task>            tasks;protected:std::mutex              _mutex;std::condition_variable _cond;
};#endif // HV_THREAD_POOL_H_class myClass{public:};class pool_task{HThreadPool *m_threadPool;std::string  my_name = "hhhhh" ;
public:pool_task(){m_threadPool = new HThreadPool(5);m_threadPool->start();}void pool_commit(){std::string param = "aaa";m_threadPool->commit([this, param] {return this->task(param); });}void task(const std::string& param){printf("aaaaaaaaaa, %s, %s\n", my_name.c_str(), param.c_str());}
};int main(){auto *p = new pool_task();p->pool_commit();getchar();return 0;
}

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