我在 Sol.h 中有以下代码,由于学校规则,大部分代码被省略了:
template <typename T,int promote = 1, typename compare = std::less<T>() >
class Sol{
private:
struct node{
T data;
struct node *next;
struct node *previous;
};
node *head, *tail;
public:
typedef unsigned int size_type;
typedef T key_type;
typedef T value_type;
size_type count;
Sol() : head(0), tail(0) {
count=0;
}
基本上它是一个类似于矢量的容器,但它做了一些我们需要模板的事情。我似乎无法获得"类型名称比较 = std::less
当我使用测试代码进行编译时,我从 Sol.h 收到两个错误,其余的都与它们有关。
>temple> g++ -Wall -Wextra -ansi -pedantic Sol.h main.cc
Sol.h:6:61: error: expected type-specifier
Sol.h:6:61: error: expected '>'
main.cc: In function 'int main()':
main.cc:19:19: error: template argument 3 is invalid
main.cc:19:24: error: invalid type in declaration before '(' token
main.cc:19:48: error: expression list treated as compound expression in initializer [-fpermissive]
main.cc:19:48: warning: left operand of comma operator has no effect [-Wunused-value]
main.cc:19:48: error: invalid conversion from 'char*' to 'int' [-fpermissive]
main.cc:20:19: error: template argument 3 is invalid
main.cc:20:31: error: expected initializer before 'it'
main.cc:22:13: error: request for member 'erase' in 'foo', which is of non-class type 'int'
main.cc:24:9: error: 'it' was not declared in this scope
main.cc:24:18: error: request for member 'find' in 'foo', which is of non-class type 'int'
main.cc:25:9: error: request for member 'end' in 'foo', which is of non-class type 'int'
main.cc:28:13: error: request for member 'find' in 'foo', which is of non-class type 'int'
main.cc:30:13: error: request for member 'find' in 'foo', which is of non-class type 'int'
main.cc: In function 'std::string cat(const T&) [with T = int, std::string = std::basic_string<char>]':
main.cc:23:24: instantiated from here
main.cc:12:35: error: 'int' is not a class, struct, or union type
main.cc:12:50: error: request for member 'end' in 'con', which is of non-class type 'const int'
main.cc:12:35: error: 'int' is not a class, struct, or union type
main.cc:12:35: error: 'int' is not a class, struct, or union type
main.cc:12:35: error: 'int' is not a class, struct, or union type
需要明确的是,第 6 行是模板行。
更改
typename compare = std::less<T>()
自
typename compare = std::less<T>
你想要一个类型,而不是一个对象。
你也必须做#include <functional>
因为这是定义std::less
的地方。