我的第一个C++类(和错误)

Question

我尝试从办公室里找到的一本书中抽取一本天真的课.

就是这个:

#include <iostream.h>
#include <math.h>

const double ANG_RAD = 0.017;

class Angulo {
  double valor;

public:
  void act_valor( double );
  double seno( void );
  double coseno( void );
  double tangente( void );
} grado;

void Angulo::act_valor( double a ) {
  valor = a;
}

double Angulo::seno(void)
{
  double temp;
  temp = sin( ANG_RAD * this.valor );
  return( temp );
}
double Angulo::coseno(void)
{
 double temp; 
 temp = cos(ANG_RAD * valor );
 return (temp);
}
double Angulo::tangente(void)
{
 return ANG_RAD * valor;
}

main()
{
 grado.act_valor( 60.0 );
 cout << "El seno del angulo es " 
      << grado.seno() << "\n";
 return(0);
}

我编译了,这是我得到的错误信息(我现在明白为什么人们抱怨C++)

In file included from /usr/include/c++/4.2.1/backward/iostream.h:31,
                 from Angulo.cc:1:
/usr/include/c++/4.2.1/backward/backward_warning.h:32:2: warning: #warning This file includes at least one deprecated or antiquated header. Please consider using one of the 32 headers found in section 17.4.1.2 of the C++ standard. Examples include substituting the <X> header for the <X.h> header for C++ includes, or <iostream> instead of the deprecated header <iostream.h>. To disable this warning use -Wno-deprecated.
Undefined symbols:
  "std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)", referenced from:
      _main in ccg0526i.o
      _main in ccg0526i.o
  "std::ios_base::Init::Init()", referenced from:
      __static_initialization_and_destruction_0(int, int)in ccg0526i.o
  "std::basic_string<char, std::char_traits<char>, std::allocator<char> >::size() const", referenced from:
      std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccg0526i.o
  "std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator[](unsigned long) const", referenced from:
      std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccg0526i.o
      std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccg0526i.o
      std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccg0526i.o
  "___gxx_personality_v0", referenced from:
      Angulo::act_valor(double)in ccg0526i.o
      Angulo::tangente()     in ccg0526i.o
      std::__verify_grouping(char const*, unsigned long, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)in ccg0526i.o
      ___tcf_0 in ccg0526i.o
      Angulo::cosen()     in ccg0526i.o
      Angulo::seno()     in ccg0526i.o
      _main in ccg0526i.o
      unsigned long const& std::min<unsigned long>(unsigned long const&, unsigned long const&)in ccg0526i.o
      __static_initialization_and_destruction_0(int, int)in ccg0526i.o
      global constructors keyed to gradoin ccg0526i.o
      CIE in ccg0526i.o
  "std::ios_base::Init::~Init()", referenced from:
      ___tcf_0 in ccg0526i.o
  "std::basic_ostream<char, std::char_traits<char> >::operator<<(double)", referenced from:
      _main in ccg0526i.o
  "std::cout", referenced from:
      _main in ccg0526i.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

有人能告诉我发生了什么事吗？

我的编译器:

Using built-in specs.
Target: i686-apple-darwin10
Configured with: /var/tmp/gcc/gcc-5664~38/src/configure --disable-checking --enable-werror --prefix=/usr --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin10 --program-prefix=i686-apple-darwin10- --host=x86_64-apple-darwin10 --target=i686-apple-darwin10 --with-gxx-include-dir=/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Apple Inc. build 5664)

我对这本旧书中的来源进行了双重和三重检查,结果是一样的.

谢谢.

Answer 1

你的书已经过时了.您正在使用的编译器更加现代化,因此它只是拒绝翻译旧的非标准代码.你很可能会以某种方式将其推向工作状态,但更新代码以使其成为标准C++会更有意义.通常,代码看起来没问题,只需要进行一些更改.

你应该使用的标题是<iostream>,而不是<iostream.h>.编译器已经告诉过你了.此外,标准库的组件现在位于命名空间中std,因此输出行main应如下所示

std::cout << "El seno del angulo es " << grado.seno() << "\n";

main 函数必须声明显式返回类型

int main()
{

C语言int默认不像C那样.

作为额外的,不那么重要的评论,没有必要像(void)在C++中那样声明无参数函数.仅仅()具有完全相同的效果.虽然如果你喜欢(void)更好,它也会起作用.此外,没有必要采取returnin 的论点().你可以说return 0;.看到不一致也很奇怪returns- 有些有()和没有().书中是这样的吗？