NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part2/11891

Text File | 1996-08-05 | 5.0 KB | 194 lines

Path: pop.gnn.com!HoangTQ
From: Tuyen Hoang <[e-mail]>
Newsgroups: comp.lang.c++
Subject: Re: Need Help With CSC Homework
Date: Sat, 16 Mar 1996 17:25:23
Organization: GNN
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pfun.cpp

//*************************************************
//**             ROMANFUN.CPP                    **
//*************************************************
//** This program will add, subtract, multiply,  **
//** and divide roman numbers. The numbers are   **
//** assumed to be less than 20 characters long. **
//** The roman numbers should not be inputed in  **
//** subtraction form. Examples - IV=6 IIII=4    **
//*************************************************
#include <iostream.h>   //for cin and cout
#include "p.h"      //has typedef and prototypes
istream& operator>>(istream& in,Romantype& x)
{
in>>x.Roman;
return in;
}

ostream& operator<<(ostream& out,Romantype x)
{
out<<x.Roman;
return out;
}

Romantype::Romantype()
{
int i;
for(i=1;i<MAXLENGTH;i++)
{
Roman[i]=' ';
}

//and Roman[MAXLENGTH]???
}

//*************************************************
//**                 ADD FUNCTION                **
//*************************************************
//** This function adds two roman numbers. It    **
//** requires a character array and two roman    **
//** numbers.                                    **
//*************************************************
void Romantype::operator+(Romantype numbertwo)
{
int numbero;
int numbert;
int answer;
Romantype answerr;
numbero=RomanToDecimal(Roman);
numbert=RomanToDecimal(numbertwo.Roman);
answer=numbero+numbert;
DecimalToRoman(answerr.Roman,answer);
cout<<answerr.Roman;
}

//*************************************************
//**     ROMAN TO DECIMAL FUNCTION               **
//*************************************************
//** This function converts a roman number to a  **
//** decimal number. It requires the character   **
//** array and the number of characters in the   **
//** array.                                      **
//*************************************************
int Romantype::RomanToDecimal(char[MAXLENGTH])
{
int number=0;               //value of number intialized to zero
int i;                      //used in for loop
for(i=1;i<MAXLENGTH;i++)          //until end of array add values of letters
{
switch(Roman[i])
{
case 'I':number=number+1;break;
case 'V':number=number+5;break;
case 'X':number=number+10;break;
case 'L':number=number+50;break;
case 'C':number=number+100;break;
case 'D':number=number+500;break;
case 'M':number=number+1000;break;
}
}
return number;    //return decimal value to where the function was called
}

//*************************************************
//**     DECIMAL TO ROMAN FUNCTION               **
//*************************************************
//** This function converts a decimal number to  **
//** a roman number. It requires a character     **
//** array and the value of the decimal number.  **
//*************************************************
void Romantype::DecimalToRoman(char[MAXLENGTH]/ *??? */ ,int answer)
                                              ^^^^name of param.?
                               ^^^^ this is a char* or a Romantype object
{
int i=1;           //used in for loop
while(answer-1000>=0) //convert to roman by storing letters in array
{
answerr.Roman[i]='M';
//^^^^^^Where does the answerr (Romantype object)   come from???
answer=answer-1000;
i++;
}
while(answer-500>=0)
{
answerr.Roman[i]='D';
answer=answer-500;
i++;
}
while(answer-100>=0)
{
answerr.Roman[i]='C';
answer=answer-100;
i++;
}
while(answer-50>=0)
{
answerr.Roman[i]='L';
answer=answer-50;
i++;
}
while(answer-10>=0)
{
answerr.Roman[i]='X';
answer=answer-10;
i++;
}
while(answer-5>=0)
{
answerr.Roman[i]='V';
answer=answer-5;
i++;
}
while(answer-1>=0)
{
answerr.Roman[i]='I';
answer=answer-1;
i++;
}
}


//Please review on
  _function_prototype_ and _parameters_passing_
  member function .

//You *miss* some important points

    1. none static member function has a hidden *this* pointer. That is
         this->Roman[i] .... so and so ...
      or just
         Roman[i] .... so and so ... ( better )

    2. Passing a variable in a function call *does not* mean you can use
that variable in the function definition.
  i.e.
   you call the function and pass 'answerr.Roman' as a parameter
DecimalToRoman(answerr.Roman,answer);
   and then you want to use 'answerr.Roman' in side the function

BIG MISTAKE

    3. You obmiss the parameter name in the function definition. Is that
your intense not to use that parameter? If I'm right, you *must* give it a
name and then use that name in side the function definition instead of
'answerr.Roman'
  Please review on function prototype and function definition: they have
different meaning and syntax