I need some help..

**FromHolland** · 05-16-2003

I am going to create my first real(tiny) program.
It will be a hexadecimal converter and it can be used to convert a value between 0 and 255 to a hexadecimal value.

Example:

normal -- hex

7 -- 7
143 -- 8f
211 -- d3
255 -- ff
etc..

For examle: When a user inputs '211', the program should return a string containing 'd3'. The program will be used to convert
hexadecimals in order to get color values used by games like Warcraft 3. The user must enter 3 values between 255 and 0, so the program will return a 6 digits hexadecimal value.

Like this:

User input: == Program returns:
255-155-55 == ff-9b-37

ONE way to do this, is by making a long, long IF statement (255)
in order to let the program return the desired value.

Due to my lack of programming experience I would like someone to tell me if there is a more efficient way..

**Brighteyes** · 05-16-2003

>For examle: When a user inputs '211', the program should return a string containing 'd3'.
>I would like someone to tell me if there is a more efficient way..
Yes, there is.

Code:

#include <iostream>
#include <iomanip>
#include <sstream>
#include <cstdlib>

using namespace std;

/*
 *  Decimal => Hexadecimal converter
 *  Copyright (c) Liz Guth 2003
 */

int main()
{
    long decimal;

    cout<<"Enter a number: "<<flush;
    if (!(cin>> decimal))
    {
        cerr<<"Whoops, invalid input";
        exit(EXIT_FAILURE);
    }

    ostringstream convert;

    convert<< hex << decimal;

    cout<<"Your number, "<< decimal <<", is "
        << convert.str() <<" in hexadecimal."<<endl;
}

**FromHolland** · 05-16-2003

I didn't know there were 'decimal' functions..
Well, I see it's not that complex. But what is this
{
cerr<<

thing?

**Brighteyes** · 05-16-2003

If the user doesn't type a number, or something freaky happens, a message is printed on the error stream and the program terminates. cerr is like cout except that it typically isn't buffered, good for error messages.

**DougDbug** · 05-16-2003

Conversion between bases only takes place during input or output. All variables are stored in binary. You can't save a number in hex. So, I don't usually use the word "convert"... I might say something like "Input as hex and display in octal format".

Of course, true conversion does take place when when you convert an ASCII string to a number.

cin and cout can use decimal, octal, or hex directly. There is a function strtoul() [string to unsigned long] that can handle input from base 2 to base 36. There is bitset (From the Standard Template Library) which can handle binary. Displaying output in "weird" bases can be more difficult, although microsoft includes the non-standard _itoa() [Integer To ASCII] function.

BTW- "I neeed some help" is a vague title. Please try to say what the topic of your question is.Board Guidelines

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