C++ 错误：“int 之前的预期主表达式”
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/9534728/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Error: "expected primary-expression before int"
提问by visanio_learner
I am getting an error: expected primary-expression before intwhen I try to return a 2 values in bool function, I think its a member function error.
我收到一个错误：int当我尝试在 bool 函数中返回 2 个值之前预期的主表达式，我认为它是一个成员函数错误。
bool binaryTreeTraversal::LeafNode(int node)
{
return (binaryTreeTraversal::LeftPtr(int node) == NULL &&
binaryTreeTraversal::RightPtr(int node) == NULL);
}
class binaryTreeTraversal
{
public:
int TreeNodes[2^5];
int size;
binaryTreeTraversal(void);
bool LeafNode(int node);
int RootNode(int node);
int LeftPtr(int node);
int RightPtr(int node);
int length();
int preOrderTraversal(int);
int inOrderTraversal(int);
int postOrderTraversal(int);
};
bool binaryTreeTraversal::LeafNode(int node)
{
return (binaryTreeTraversal::LeftPtr(node) == NULL &&
binaryTreeTraversal::RightPtr(node) == NULL);
}
回答by Raymond Chen
Making this question useful to others: "expected primary-expression" means "I thought you were going to put an expression here."
让这个问题对其他人有用：“预期的主要表达”的意思是“我以为你会在这里放一个表达。”
An expression is an object, a function call, or operators applied to objects and function calls . For example, x + f(y)is an expression involving variables xand y, the function fand the operator +.
表达式是一个对象、一个函数调用或应用于对象和函数调用的运算符。例如，x + f(y)是一个涉及变量x和y、函数f和运算符的表达式+。
There are many types of expressions, but the distinction isn't important for the purpose of this error message.
有多种类型的表达式，但对于此错误消息的目的而言，区别并不重要。
After the open-parenthesis denoting a function call, you are expected to enter an expression, representing the value to pass as a parameter to the function call. But instead, the compiler saw the word int, which is not a variable or a function or an operator.
在表示函数调用的左括号之后，您需要输入一个表达式，表示作为参数传递给函数调用的值。但相反，编译器看到了单词int，它不是变量、函数或运算符。
回答by hmjd
Change:
改变：
return (binaryTreeTraversal::LeftPtr(int node) == NULL &&
binaryTreeTraversal::RightPtr(int node) == NULL);
to:
到：
return (binaryTreeTraversal::LeftPtr(node) == NULL &&
binaryTreeTraversal::RightPtr(node) == NULL);
EDIT:
编辑：
The return type from LeftPtr()and RightPtr()is int:
从返回类型LeftPtr()和RightPtr()是int：
class binaryTreeTraversal
{
public:
...
bool LeafNode(int node)
{
return (binaryTreeTraversal::LeftPtr(node) == 0 &&
binaryTreeTraversal::RightPtr(node) == 0);
}
};
or:
或者：
class binaryTreeTraversal
{
public:
...
bool LeafNode(int node)
{
return (!binaryTreeTraversal::LeftPtr(node) &&
!binaryTreeTraversal::RightPtr(node));
}
};
or as LeftPtr()and RightPtr()are not virtual:
或作为LeftPtr()和RightPtr()不是virtual：
class binaryTreeTraversal
{
public:
...
bool LeafNode(int node)
{
return (!LeftPtr(node) && !RightPtr(node));
}
};
回答by Stefan Birladeanu
return (binaryTreeTraversal::LeftPtr(int node) == NULL &&
binaryTreeTraversal::RightPtr(int node) == NULL);
return (binaryTreeTraversal::LeftPtr( int node) == NULL &&
binaryTreeTraversal::RightPtr( int node) == NULL);
//remove int from bolded part
//从粗体部分删除int
回答by rob05c
return (binaryTreeTraversal::LeftPtr(int node) == NULL && binaryTreeTraversal::RightPtr(int node) == NULL);
should be
应该
return (binaryTreeTraversal::LeftPtr(node) == NULL && binaryTreeTraversal::RightPtr(node) == NULL);
回答by spmno
bool binaryTreeTraversal::LeafNode(int node)
{
return ((LeftPtr(node) == NULL) && (RightPtr(node) == NULL));
}
