NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part2/11934

Internet Message Format | 1996-08-05 | 5.5 KB

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 22:33:58
Organization: GNN
Message-ID: <4ig14c$[e-mail]>
References: <4g0qun$[e-mail]>
NNTP-Posting-Host: www-29-26.gnn.com
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
X-GNN-NewsServer-Posting-Date: 17 Mar 1996 03:32:28 GMT
X-Mailer: GNNmessenger 1.2


> Troy code:
>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]=' ';
>}
>}
>
>//*************************************************
>//**                 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)
//                                                ^^^what is the name of param. ?
//are you sure what you want to do?
//without the param.'s name  the char array you pass in will be *thrown away*.

>{
>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?
// Do you mean you pass the 'answerr.Roman' in the function call
//then you can use it here?

>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++;
>}
>}
>

/* There are some important points

    1. none static member function has a hidden *this* pointer. That is
         this->Roman[i] .... so and so ...( not recommented )
      or just
         Roman[i] .... so and so ... ( better )
    then you do not need passing a char[] to access the Roman char array

    2. Passing a variable  in a function call *does not* mean you can use
    that variable's name in the function definition body.
  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' name in side the function    body
    this is a 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' or better yet throw it away and get familiar with 'this*'-see #1.

//Please review on your note or textbook
  function prototype and function definition, they have
        different meaning and different syntax

  function calling and parameters passing
  member function and this pointer .
*/
Hoang Tuyen Q.
[e-mail]