How to compare all similar variable names in once

Question

1.00/5 (1 vote)

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C++

#include <iostream>

using namespace std;

int main()
{
    int a;
int my_name=1;
int my_class=5;
int my_age=3;
cout<<"enter the number"<<endl;
cin>>a;
if (a==my_*){
    cout<<"success";
}

}

What I have tried:

any other shortcut process, except this

C++

if ((a==my_name)&&(a==my_class)&&(a==my_age)){
    cout<<"success";

Posted 18-Nov-20 18:54pm

Gautam Naresh

Updated 18-Nov-20 20:17pm

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Rick York · Accepted Answer · 2020-11-18T19:14:00

BTW - With the values you have assigned those variables your "shortcut" condition will never be true.

I find macros to be helpful in situations like this. They can definitely be abused in evil ways but they can also be quite useful. Here's how I would do this :

C++

using PCTSTR = const char *;

bool CompVarValues( PCTSTR varname, int value1, int value2 )
{
   bool state = ( value1 == value2 );
   PCTSTR boolstr = state ? "true" : "false";
   std::cout << "comparing value of " << varname << " result is " << boolstr << std::endl;
}

// a macro to help with this - it uses the string-izing operator #

#define CompareValues( a, b )  CompVarValues( #a, a, b )

// usage :

CompareValues( my_name, a );
CompareValues( my_class, a );
CompareValues( my_age, a );

CPallini · Accepted Answer · 2020-11-18T20:17:00

You might, for instance, iterate over a container

C++

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

int main()
{
  int a;

  unordered_map<string, int> um = { {"my_name", 1}, {"my_class", 5}, {"my_age", 3} };

  cout<<"enter the number"<< endl;
  cin >> a;

  unsigned matches = 0;

  for (auto p : um )
    if ( p.second == a)
      ++matches;

  if ( matches == um.size() )
    cout << "success" << endl;
  else
    cout << "failure, matches " << matches << "/" << um.size() << endl;

}

How to compare all similar variable names in once

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