Application Development

Appendix C. Panther Java Calculator

This appendix contains the development notes for the Panther Java Calculator sample that is located at $SMBASE/samples/javacalc.

Repository Contents

The repository, calc.dic, contains the following items.

**Table C-1 Lower Buttons**
Repository Name	Function	Java Class
`num_pb`	Numeric Keys (also period and +/-)	`CalcNum`
`op_pb`	Arithmetic operations	`CalcFunc2`
`mem_pb`	Memory functions	`CalcMem`
`misc_pb`	Miscellaneous operations (Constants, Clear, backspace)	`CalcMisc`

**Table C-2 Upper Buttons**
Repository Name	Function	Java Class
`trig_pb`	Trigonometric functions	`CalcTrig`
`mode_pb`	Mode change	`CalcMode`
`func1_pb`	Single operand functions	`CalcFunc1`
`func2_pb`	Two operand functions	`CalcFunc2`

Calculator Screen

The calculator screen, calc.scr, contains the following widgets and settings.

**Table C-3 Screen Properties**
Property	Setting
IDENTITYTitle	Calculator
IDENTITYJava Tag	CalcScreen
HELPHelp Screen	help.scr
FOCUS->JPL Procedures	`global register, memory, operation, op_just_done, degrees, currency` `register`: Holds the "invisible" operand (last number entered before performing operation) `memory`: storage for M+, MR, MC function `operation`: Storage of the last 2 operand operation key pressed `op_just_done`: Used to determine if next number entered should clear display first. `degrees`: flag for trig operations, 1=degrees, 0=radians `currency`: flag for display, 1=fixed decimal (2) places, 0=floating decimal

**Table C-4 Display Widgets**
Widget Name	Widget Type	Function	Java Class
mode_display	Dynamic Label	Displays modes degrees / radians, currency / normal	None
display	Single line text	Calculator display	None

The following table lists the types of push buttons, their names, the push button they inherit from in the repository and the java class.

**Table C-5 Button Widgets**
Type	Name	Inherit From	Java Class
Digits: 0,1,2,3,4,5,6,7,8,9	n`X`_pb (where `X` is the digit)	Num_pb	CalcNum (Inherited)
. (period)	dot_pb	Num_pb	CalcNum (Inherited)
+/-	sign_pb	Sign_pb	CalcFunc1
C, CE	c_pb, ce_pb	misc_pb	CalcMisc (Inherited)
*, /	mult_pb, div_pb	op_pb	CalcFunc2 (Inherited)
+, -	plus_pb, minus_pb	op_pb	CalcFunc2 (Inherited)
= (Equals)	equls_pb	op_pb (size changed)	CalcFunc2 (Inherited)
MC, MR	mc_pb, mr_pb	mem_pb	CalcMem (Inherited)
M+	mp_pb	mem_pb	CalcMem (Inherited)
Pi	pi_pb	misc_pb	CalcMisc (Inherited)
_ (Backspace)	bs_pb	misc_pb	CalcMisc (Inherited)
Dg/Rd	angle_pb	mode_pb	CalcMode (Inherited)
#/$	currency_pb	mode_pb	CalcMode (Inherited)
X^Y, Mod	power_pb, mod_pb	func2_pb	CalcFunc2 (Inherited)
Sin, Cos, Tan, Atan	sin_pb, cos_pb, tan_pb, atan_pb	trig_pb	CalcTrig (Inherited)
1/x (Inverse)	inv_pb	func1_pb	CalcFunc1 (Inherited)
Sqrt (Square root)	sqr_pb	func1_pb	CalcFunc1 (Inherited)
Log, Exp	log_pb, exp_pb	func1_pb	CalcFunc1 (Inherited)

Java Classes

The Java classes have been broken into handlers which handle either screen entry or "classes" of buttons. This is a mid-way point between having a separate class for each button and having a single class handle all the buttons.

CalcScreen:

Implements ScreenHandler interface

Screen entry function. Initialize global variables and allow backspace, delete and Newline to be caught by ButtonHandler.

Screen exit function. Release backspace, delete, and Newline, restoring normal behavior for those keys.

CalcFunc1:

Implements ButtonHandler interface.

Handles all single operand calculator functions (like Sqrt functions). Also handles the Sign toggle (+/-)

CalcFunc2:

Implements ButtonHandler interface

Handles all dual operand calculator functions. This class actually performs the last stored operation, and stores the next operation in the global variable "operation."

Implements ButtonHandler interface

Handles all memory functions.

CalcMisc:

Implements ButtonHandler interface

Handles C, CE, backspace and Pi button.

CalcMode:

Implements ButtonHandler interface

Handle mode switching buttons, "Deg/Rad" and "#/$"

CalcTrig:

Implements ButtonHandler interface.

Even though these functions are similar to the CalcFunc1 operations, these make use of the "degrees" setting, so a separate class was created.

Implements ButtonHandler interface.

Handles all numeric keys, and period.