currency calculatordlg.cpp

计算器 英国一个学生写的 代码很适合学习

		if( m_curr_or_num==IDC_CURRENCY )
		{
			m_amount += ' ';
			m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
		}
		CWnd::SetDlgItemText( IDC_RESULT, m_amount );
		new_num_flag = false;
		return;
	}
	if( m_amount.GetLength()>=MAX_LENGTH )
		return;
	if( m_amount[0]=='0' && m_amount.Find('.')==-1 )
		m_amount.Delete( 0, 1 );
	m_amount += '7';
	if( m_curr_or_num==IDC_CURRENCY )
	{
		m_amount += ' ';
		m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
	}
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );
}

void CCurrencyCalculatorDlg::OnNum8() 
{
	if( m_amount.Find( ' ' )!=-1 )
		m_amount = remove_c_letter();
	if( new_num_flag )
	{
		m_amount = '8';
		if( m_curr_or_num==IDC_CURRENCY )
		{
			m_amount += ' ';
			m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
		}
		CWnd::SetDlgItemText( IDC_RESULT, m_amount );
		new_num_flag = false;
		return;
	}
	if( m_amount.GetLength()>=MAX_LENGTH )
		return;
	if( m_amount[0]=='0' && m_amount.Find('.')==-1 )
		m_amount.Delete( 0, 1 );
	m_amount += '8';
	if( m_curr_or_num==IDC_CURRENCY )
	{
		m_amount += ' ';
		m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
	}
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );
}

void CCurrencyCalculatorDlg::OnNum9() 
{
	if( m_amount.Find( ' ' )!=-1 )
		m_amount = remove_c_letter();
	if( new_num_flag )
	{
		m_amount = '9';
		if( m_curr_or_num==IDC_CURRENCY )
		{
			m_amount += ' ';
			m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
		}
		CWnd::SetDlgItemText( IDC_RESULT, m_amount );
		new_num_flag = false;
		return;
	}
	if( m_amount.GetLength()>=MAX_LENGTH )
		return;
	if( m_amount[0]=='0' && m_amount.Find('.')==-1 )
		m_amount.Delete( 0, 1 );
	m_amount += '9';
	if( m_curr_or_num==IDC_CURRENCY )
	{
		m_amount += ' ';
		m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
	}
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );
}

void CCurrencyCalculatorDlg::OnPoint() 
{
	if( m_amount.Find( ' ' )!=-1 )
		m_amount = remove_c_letter();
	if( new_num_flag )
	{
		m_amount = "0.";
		if( m_curr_or_num==IDC_CURRENCY )
		{
			m_amount += ' ';
			m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
		}
		CWnd::SetDlgItemText( IDC_RESULT, m_amount );
		new_num_flag = false;
		return;
	}
	if( m_amount.GetLength()>=MAX_LENGTH )
		return;
	if( m_amount.Find('.')!=-1 )
		return;
		m_amount += '.';
	if( m_curr_or_num==IDC_CURRENCY )
	{
		m_amount += ' ';
		m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
	}
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );
}

void CCurrencyCalculatorDlg::OnBackspace() 
{	// remove currency letter if it is currency
	if( m_amount.Find( ' ' )!=-1 )
		m_amount = remove_c_letter();
	if( m_amount=="0" )
		return;				// return if already 0
	if( m_amount.GetLength()==1 )
		m_amount = "0";		// make result 0, if only one number exists
	else					// delete last number
		m_amount.Delete( m_amount.GetLength()-1, 1 );
	if( m_curr_or_num==IDC_CURRENCY )
	{	// add currency letter if it is currency
		m_amount += ' ';
		m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
	}
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );	// up-date result field
}

void CCurrencyCalculatorDlg::OnClear() 
{	// remove currency letter if it is currency
	if( m_amount.Find( ' ' )!=-1 )
		m_amount = remove_c_letter();
	if( m_amount=="0" )
		return;				// return if already 0
	m_amount = "0";			// make result 0
	if( m_curr_or_num==IDC_CURRENCY )
	{	// add currency letter if it is currency
		m_amount += ' ';
		m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
	}
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );	// up-date result field
}

void CCurrencyCalculatorDlg::OnClearall() 
{	// remove currency letter if it is currency
	if( m_amount.Find( ' ' )!=-1 )
		m_amount = remove_c_letter();
	m_amount = "0";			// make result 0
	if( m_curr_or_num==IDC_CURRENCY )
	{	// add currency letter if it is currency
		m_amount += ' ';
		m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
	}
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );	// up-date result field
	last_op = none;			// make last operation null
	new_num_flag = false;	// turn new number flag OFF
	if( first_num.curr_flag )	// make first number 0
		first_num.curr_num.set_currency( 0.0f, Currency::get_c_letter( COUNTRIES[m_cur_sel] ) );
	else
		first_num.doub_num = 0.0f;
	intermediate_num.make_null();	// make intermediate_num null
}

void CCurrencyCalculatorDlg::OnAdd() 
{	// convert m_amount into double after removing currency letter if it is currency
	CString str;
	if( m_amount.Find( ' ' )!=-1 )
		str = remove_c_letter();
	else
		str = m_amount;
	double num = atof( str );
	if( num==0 )
		return;		// return if 0
	last_op = addition;		// make addition last operation
	new_num_flag = true;	// turn new number flag ON
	if( m_curr_or_num==IDC_CURRENCY )
	{						// save it as first number
		first_num.curr_flag = true;
		first_num.curr_num.set_currency( num, Currency::get_c_letter( COUNTRIES[m_cur_sel] ) );
	}
	else
	{
		first_num.curr_flag = false;
		first_num.doub_num = num;
	}
	intermediate_num.make_null();	// make intermediate_num null to indicate fresh operation
}

void CCurrencyCalculatorDlg::OnSubtract() 
{
	CString str;
	if( m_amount.Find( ' ' )!=-1 )
		str = remove_c_letter();
	else
		str = m_amount;
	double num = atof( str );
	if( num==0 )
		return;
	last_op = subtraction;
	new_num_flag = true;
	if( m_curr_or_num==IDC_CURRENCY )
	{
		first_num.curr_flag = true;
		first_num.curr_num.set_currency( num, Currency::get_c_letter( COUNTRIES[m_cur_sel] ) );
	}
	else
	{
		first_num.curr_flag = false;
		first_num.doub_num = num;
	}
	intermediate_num.make_null();
}

void CCurrencyCalculatorDlg::OnMultiply() 
{
	CString str;
	if( m_amount.Find( ' ' )!=-1 )
		str = remove_c_letter();
	else
		str = m_amount;
	double num = atof( str );
	if( num==0 )
		return;
	last_op = multiplication;
	new_num_flag = true;
	if( m_curr_or_num==IDC_CURRENCY )
	{
		first_num.curr_flag = true;
		first_num.curr_num.set_currency( num, Currency::get_c_letter( COUNTRIES[m_cur_sel] ) );
		CWnd::CheckRadioButton( IDC_CURRENCY, IDC_NUMBER, IDC_NUMBER );
		OnNumber();	// check Number, as one operand of multiply should be a Number
	}
	else
	{
		first_num.curr_flag = false;
		first_num.doub_num = num;
	}
	intermediate_num.make_null();
}

void CCurrencyCalculatorDlg::OnDivide() 
{
	CString str;
	if( m_amount.Find( ' ' )!=-1 )
		str = remove_c_letter();
	else
		str = m_amount;
	double num = atof( str );
	if( num==0 )
		return;
	last_op = division;
	new_num_flag = true;
	if( m_curr_or_num==IDC_CURRENCY )
	{
		first_num.curr_flag = true;
		first_num.curr_num.set_currency( num, Currency::get_c_letter( COUNTRIES[m_cur_sel] ) );
		CWnd::CheckRadioButton( IDC_CURRENCY, IDC_NUMBER, IDC_NUMBER );
		OnNumber();	// check Number, as one operand of divide should be a Number
	}
	else
	{
		first_num.curr_flag = false;
		first_num.doub_num = num;
	}
	intermediate_num.make_null();
}

void CCurrencyCalculatorDlg::OnEqual() 
{
	if( last_op==none )
		return;		// return, if no last operation exists
	// check intermediate_num. If it is null, take 2nd operand from result field
	if( intermediate_num.is_null() )
	{	// convert m_amount into double after removing currency letter if it is currency
		CString str;
		if( m_amount.Find( ' ' )!=-1 )
			str = remove_c_letter();
		else
			str = m_amount;
		double num = atof( str );
		if( num==0 )
			return;		// return, if number is 0
		// save it as second number
		num_currency second_num;
		if( m_curr_or_num==IDC_CURRENCY )
		{
			second_num.curr_num.set_currency( num, 
				Currency::get_c_letter( COUNTRIES[m_cur_sel] ) );
			second_num.curr_flag = true;
		}
		else
		{
			second_num.doub_num = num;
			second_num.curr_flag = false;
		}
		intermediate_num = second_num;		// set this to intermediate_num
	}
	BOOL flag = do_operation( intermediate_num );	// perform the required operation
	if( !flag )
	{	// if last operation was unsuccessful (due to two multiplication & division of two
		// currency amounts, add currency letter as it would be not added by make string()
		m_amount = "0 ";
		if( m_curr_or_num==IDC_CURRENCY )
			m_amount += Currency::get_c_letter( COUNTRIES[m_cur_sel] );
		OnClearall();		// clear all inputs
	}
	// otherwise, set amount from result and up-date result field
	else if( result.curr_flag )
		m_amount = result.curr_num.make_string();
	else
		dbl_to_text( result.doub_num, m_amount );
	CWnd::SetDlgItemText( IDC_RESULT, m_amount );
	if( result.curr_flag && m_curr_or_num==IDC_NUMBER )
	{	// if result is in currency & number radio button is selected, (it will happen during * & / operations)
		CWnd::CheckRadioButton( IDC_CURRENCY, IDC_NUMBER, IDC_CURRENCY );
		OnCurrency();	// check Currency radio button
	}
	first_num = result;				// make result now the first_num for next equal operation
	new_num_flag = true;			// turn new number flag ON
}

void CCurrencyCalculatorDlg::OnAbout() 
{
	CAboutDlg dialog;
	dialog.DoModal();
}

void CCurrencyCalculatorDlg::OnExit() 
{
	CCurrencyCalculatorDlg::OnOK();
}

/////////////////////////////////////////////////////////////////////////////
// CCurrencyCalculatorDlg member functions

CString CCurrencyCalculatorDlg::remove_c_letter()
{	// remove currency letter from m_amount and return new string
	CString temp_string = m_amount;		// m_amount will remain unchanged
	int length = temp_string.GetLength();
	int index = temp_string.Find( ' ' );
	if( index!=-1 )
		temp_string.Delete( index, length-index );
	return temp_string;
}

void CCurrencyCalculatorDlg::dbl_to_text( double value, CString &str )
{
	int decimal, sign;
	str = fcvt( value, PRECISION, &decimal, &sign );
	// handle invalid precision
	if( value<1.0 && str.GetLength()!=PRECISION )
	{
		int diff = PRECISION - str.GetLength();
		for( int j=0; j<diff; j++ )
			str.Insert(0, "0" );
	}
	// insert "0", "." & "-" at appropriate position
	if( str=="" )
		str = "0.0";
	else
	{
		str.Insert(decimal, ".");
		if( value<1.0 )
			str.Insert(0, "0");
		if( sign )
			str.Insert(0, "-");
	}
}

BOOL CCurrencyCalculatorDlg::do_operation( num_currency second_num )
{	// if currencies are different, convert currency of 1st number into currency of 2nd
	if( first_num.curr_flag && second_num.curr_flag )
		if( first_num.curr_num.get_c_letter()!=second_num.curr_num.get_c_letter() )
			first_num.curr_num = Currency::convert_currency( first_num.curr_num,
				first_num.curr_num.get_c_letter(), second_num.curr_num.get_c_letter() );
	BOOL flag = true;		// true flag for operations by default
	switch( last_op )
	{
	case addition:
		if( !first_num.curr_flag && !second_num.curr_flag )
		{	// both numbers are double (simple double arithematic is used)
			result.curr_flag = false;
			result.doub_num = first_num.doub_num + second_num.doub_num;
		}
		else if( !first_num.curr_flag && second_num.curr_flag )
		{	// 1st number is double & 2nd is currency (overloaded + operator with
			result.curr_flag = true;	// double number is used)
			result.curr_num = second_num.curr_num + first_num.doub_num;
		}
		else if( first_num.curr_flag && !second_num.curr_flag )
		{	// 1st number is currency & 2nd is double (overloaded + operator with
			result.curr_flag = true;	// double number is used)
			result.curr_num = first_num.curr_num + second_num.doub_num;
		}
		else
		{	// both numbers are currency (overloaded + operator with Currency is used)
			result.curr_flag = true;
			result.curr_num = first_num.curr_num + second_num.curr_num;
		}
		break;
	case subtraction:
		if( !first_num.curr_flag && !second_num.curr_flag )
		{
			result.curr_flag = false;
			result.doub_num = first_num.doub_num - second_num.doub_num;
		}
		else if( !first_num.curr_flag && second_num.curr_flag )
		{
			result.curr_flag = true;
			double num = first_num.doub_num - second_num.curr_num.get_double();
			if( num<0 )			// if result is negative
			{
				::AfxMessageBox( "Cannot subtract highr amount from lower amount..." );
				flag = false;	// show error message and set flag false
			}
			else
				result.curr_num.set_currency( num, second_num.curr_num.get_c_letter() );
		}
		else if( first_num.curr_flag && !second_num.curr_flag )
		{
			result.curr_flag = true;
			result.curr_num = first_num.curr_num - second_num.doub_num;
			if( !first_num.curr_num.get_op_flag() )	// if subtraction was not successful
				flag = false;	// set flag false (overloaded - operator will show error message
		}
		else
		{
			result.curr_flag = true;
			result.curr_num = first_num.curr_num - second_num.curr_num;
			if( !first_num.curr_num.get_op_flag() )
				flag = false;
		}
		break;
	case multiplication:
		if( !first_num.curr_flag && !second_num.curr_flag )
		{
			result.curr_flag = false;
			result.doub_num = first_num.doub_num * second_num.doub_num;
		}
		else if( !first_num.curr_flag && second_num.curr_flag )
		{
			result.curr_flag = true;
			result.curr_num = second_num.curr_num * first_num.doub_num;
		}
		else if( first_num.curr_flag && !second_num.curr_flag )
		{
			result.curr_flag = true;
			result.curr_num = first_num.curr_num * second_num.doub_num;
		}
		else
		{	// multiplication not allowed for two currency amounts
			::AfxMessageBox( "Can not multiply two Currency Amounts. One operand should be a number..." );
			flag = false;
		}
		break;
	case division:
		if( !first_num.curr_flag && !second_num.curr_flag )
		{
			result.curr_flag = false;
			result.doub_num = first_num.doub_num / second_num.doub_num;
		}
		else if( !first_num.curr_flag && second_num.curr_flag )
		{
			result.curr_flag = true;
			double num = first_num.doub_num / second_num.curr_num.get_double();
			result.curr_num.set_currency( num, second_num.curr_num.get_c_letter() );
		}
		else if( first_num.curr_flag && !second_num.curr_flag )
		{
			result.curr_flag = true;
			result.curr_num = first_num.curr_num / second_num.doub_num;
		}
		else
		{	// division not allowed for two currency amounts
			::AfxMessageBox( "Can not divide two Currency Amounts. Divisor should be a number..." );
			flag = false;
		}
		break;
	}
	return flag;
}