Question

I have this code from programming pearls

#include <iostream>
//#include <string>
using namespace std;
template <class T>
void measure(char *text)
{
    cout<<"measure"<<text<<"\t";
    cout<<sizeof(t)<<"\n";
}
#define MEASURE(T,text){
cout<<text<<"\t";
 cout<<sizeof(T)<<"\t";
 int lastp=0;
  for (int i=0;i<11;i++){
      T *p=new T;
      int thisp=(int)p;
       if (lastp!=0)
            cout<<" "<<thisp-lastp;
       lastp=thisp;
  }
  cout<<"n":
  }

int main(){

     return 0;
}

but there are some mistakes

1>------ Build started: Project: new_practises, Configuration: Debug Win32 ------
1>  practises.cpp
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(11): error C2143: syntax error : missing ';' before '<<'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(11): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(12): error C2143: syntax error : missing ';' before '<<'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(12): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(12): error C2086: 'int cout' : redefinition
1>          c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(11) : see declaration of 'cout'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2059: syntax error : 'for'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2143: syntax error : missing ')' before ';'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2143: syntax error : missing ';' before '<'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2143: syntax error : missing ';' before '++'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2086: 'int i' : redefinition
1>          c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14) : see declaration of 'i'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2059: syntax error : ')'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2143: syntax error : missing ';' before '{'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(14): error C2447: '{' : missing function header (old-style formal list?)
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(21): error C2143: syntax error : missing ';' before '<<'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(21): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(21): error C2086: 'int cout' : redefinition
1>          c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(11) : see declaration of 'cout'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(22): error C2059: syntax error : '}'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(22): error C2143: syntax error : missing ';' before '}'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(22): error C2059: syntax error : '}'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(24): error C2143: syntax error : missing ';' before '{'
1>c:\users\david\documents\visual studio 2010\projects\new_practises\practises.cpp(24): error C2447: '{' : missing function header (old-style formal list?)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

What do I need to fix?

Answer 1

In addition to Stephen’s answer, I can say that #define is un-C++ish. It becomes useful when you need a variable name that corresponds to a string or something the like. For mostly all other cases, use functions.

Next to that, I must concur with DeadMG’s opinion that at least I’m too stupid to see any reason to write this function. But that’s another concern 🙂

If you actually want to measure the length of a string, you can use the function strlen.

What your MEASURE seems to do is print out a series of 11 newly allocated memory addresses. Nice to do when you are studying the memory allocation strategy of your runtime, but otherwise not too useful.

Also don’t forget to delete what you have newed.

#define MEASURE(T,text) {\
    cout<<text<<"\t";\
    cout<<sizeof(T)<<"\t";\
    ...

can be directly translated into a template function: way easier to write, and to debug.

template< typename T > // assuming you _need_ a variable type of arguments
void MEASURE( const T& text) {
    cout<<text<<"\t";
    cout<<sizeof(T)<<"\t"; 
    // will write the size of e.g. one character.  Maybe
    // you should use strlen or the like...
    int lastp=0;
    for (int i=0;i<11;i++){
        T *p=new T;
        int thisp=(int)p;
        if (lastp!=0) cout<<" "<<thisp-lastp;
        lastp=thisp;
    }
    cout<<"n";
}