编译错误：尝试在函数调用中指定参数类型时出现“预期在 ' ' 之前出现主表达式”

当我编译我的程序时，我收到以下错误消息：

stringPerm.cpp: In function ‘int main()’:
stringPerm.cpp:12: error: expected primary-expression before ‘word’

我尝试在将变量分配给函数之前在单独的行上定义变量，但最终得到了相同的错误消息。

原因是什么？如何解决该问题？

这是代码：

#include <iostream>
#include <string>
using namespace std;

string userInput();
int wordLengthFunction(string word);
int permutation(int wordLength);

int main()
{
    string word = userInput();
    int wordLength = wordLengthFunction(string word);

    cout << word << " has " << permutation(wordLength) << " permutations." << endl;
    
    return 0;
}

string userInput()
{
    string word;

    cout << "Please enter a word: ";
    cin >> word;

    return word;
}

int wordLengthFunction(string word)
{
    int wordLength;

    wordLength = word.length();

    return wordLength;
}

int permutation(int wordLength)
{    
    if (wordLength == 1)
    {
        return wordLength;
    }
    else
    {
        return wordLength * permutation(wordLength - 1);
    }    
}

您的调用中不需要“字符串”wordLengthFunction().

int wordLength = wordLengthFunction(string word);

应该

int wordLength = wordLengthFunction(word);