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Sample Programs from NeXSTEP 3.3

/*
 *	SimpleCalc -- Randy Nelson
 *	A general class that directly supports a calculator interface
 *	Created 8-8-90
 *
 *	You may freely copy, distribute and reuse the code in this example.
 *	NeXT disclaims any warranty of any kind, expressed or implied, as to
 *	its fitness for any particular use.
 */

#import <objc/Object.h>

@interface SimpleCalc:Object
{
    id	infoPanel;
    id	helpPanel;
    
    id 	display;	/* a text object -- to show the output and input */

    id 	enterKey;	/* outlet to set the key equivalents */
    
    id 	stringSet;	/* our string external to the source */
    
    int 	operator;	/* represents the current operator or zero */
    
    double 	accumulator;	/* a buffer to hold the first number entered */
    
    BOOL    numberHasADecimal,
	    startingSecondNumber,
	    treatingOperationKeyLikeEqualKey,
	    noFirstNumber;	/* flags that describe the calculators state */
}

- doInit;
/* initialize an instance of the class and its flags for start-up
 * also used by the clear all key
 */

- numberKeys:sender;
/* sent by any number key or the decimal point key in the interface (0-9, .)
 * appends the character to display using appendToDisplay:
 * erases the previous number if startingSecondNumber
 */

- numberDirectFromDisplay:sender;
/* sent as the action of displayer -- allows direct entry of numbers
 * startingSecondNumber gets YES
 */
 
- equalsKey:sender;
/* sent by the equals key in the interface (=)
 * at this point accumulator holds the first number
 * operator holds an int defined to an operation
 * displayer hold the second number
 * performs the operation and leaves the result in the dsplayer
 */

- operationKeys:sender;
/* sent by the operation keys in the interface (+, -, * and /)
 * sets the value of operation
 * acts like equals to chain a calculation when
 * treatingOperationKeyLikeEqualKey
 */
 
- clearKeys:sender;
/* sent by either clear key in the interface(clear, clear all)
 * clear -- zeros the display -- allows re-enetering a number
 * clear all -- resets by calling init
 */

- decimal;
/* called by numberKeys: when it finds the number is a decimal point
 * checks first if numberHasADecimal already
 * if not -- appendToDisplay: a decimal point
 */
 
- appendToDisplay:(const char *)theDigit;
/* sent by objects wanting to append a digit to the number in the displayer
 * removes the leading zeros a zero value displayer has
 * unless there is a decimal point
 */
 
- appDidInit:sender;
/* handles some key equivalent setting and orders the window front
 * should be Application's delegate to receive
 */

- windowWillClose:sender;
/* quits app when window is closed
 * for example -- app's quit menu item can send performClose: to window
 * should be Window's delegate to receive
 */
 
- infoPanel:sender;
- helpPanel:sender;
/* sent by the menu in interface
 * creates the panels as they are needed
 */
@end

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