Help with writing a function

**thatdude** · 11-14-2003

I am trying to write a function that will take input from the user and compare it to a list of valid entries.

Code:

#include <iostream.h>

char GetChoice(const String, &LegalChoices);

/*Forces the user to enter a character in LegalChoices and returns it
  Post: Character in ValidChoices returned							*/

char *ValidChoices = "ABCabc";

char GetChoice(char *ValidChoices)
{
 char Choice;
 int cx;
 int valid = FALSE;

 while (!valid)
 {
  cout<<"Enter your choice (A, B, or C):";
  cin>>Choice;

  cx = 0;
  while (ValidChoices[cx] != '\0')
  {
   if (Choice == ValidChoices[cx])
   {
    valid = TRUE;
    break;
   }
   cx ++;
  }
  if (!valid) "Invalid Choice";
 }

 return Choice;
}

This is the code I am trying to use in the function. I am getting 3 errors:

Error in this line

Code:

char GetChoice(const String, &LegalChoices);

This line

Code:

 int valid = FALSE;

and this line

Code:

valid = TRUE;

I don't see what I am missing maybe because I have been staring at this for a few hours. Can someone point what I am doing wrong? Or if there is a better way for me to do this. i am using this in many sections of my code and I am just trying to make this easier then writing it multiple times.

**bennyandthejets** · 11-14-2003

What errors are you getting?

EDIT: I just noticed, change this:

Code:

char GetChoice(const String &LegalChoices);

You had a comma in there.

**Prelude** · 11-14-2003

There's plenty wrong with this, mostly in your prototype and definition. Then there's the fact that FALSE and TRUE haven't been defined. Try something like this:

Code:

#include <iostream>

char getChoice ( const char *valid )
{
  char c = 0;
  bool done = false;

  while ( !done && std::cin.get ( c ) ) {
    for ( const char *p = valid; *p != '\0'; p++ ) {
      if ( c == *p ) {
        done = true;
        break;
      }
    }
  }

  return c;
}

int main()
{
  std::cout<< getChoice ( "ABCabc" ) <<std::endl;
}

Or if you can stand using the STL:

Code:

#include <iostream>
#include <algorithm>

char getChoice ( const char *valid, int size )
{
  char c;
  const char *end = valid + size;

  while ( std::cin.get ( c ) ) {
    if ( std::find ( valid, end, c ) != end )
      return c;
  }

  return 0; // Or another suitable failure value
}

int main()
{
  std::cout<< getChoice ( "ABCabc", 6 ) <<std::endl;
}

**thatdude** · 11-14-2003

Thanks for the help. Those options are a much better way I think. Mine was kind of the extra long way.

**Omnius** · 11-14-2003

Code:

#include <iostream>
#include <string>
#include <limits>

using namespace std;

char getChoice()
{
    string validChoices("abcABC");
    char userInput;
    while(true){
        cout << "Enter a character: " << flush;
        cin >> userInput;
        cin.ignore( numeric_limits<streamsize>::max(), '\n' );
        if(validChoices.find(userInput) != string::npos){
            return userInput;
        } else {
            cout << "Invalid choice. ";
        }
    }
}

int main()
{
    char userSelection = getChoice();
    cout << "You entered: " << userSelection << endl;
}

Thread: Help with writing a function

Thread Tools

Search Thread

Display

Help with writing a function

Similar Threads

Seg Fault in Compare Function

In over my head

We Got _DEBUG Errors

const at the end of a sub routine?

airport Log program using 3D linked List : problem reading from file