RPN Calculus - The Scientific RPN Calculator for the iPad

Memory
Area

Stack
Area

Memory
Area

Stack
Area

Landscape Mode

Portrait Mode

Introduction

RPN Calculus is a scientific RPN Calculator for the Apple iPad. RPN Calculus provides basic arithmetic operations as well as advanced mathematic operations like trigonometric, hyperbolic or logarithmic functions. The calculator app provides an unlimited amount (well, limited by system resources) of memory space for values.

RPN Calculus performs calculations with a precision of up to 15 digits and supports a number rage from -1E127 to 1E127. It's smallest presentable number is 1E-128.

Performing Basic Calculations

RPN Calculus follows the reverse polish notation (RPN). This means, the calculation operants must be put on the stack before they can be part of a calculation. For example, if you want to add the values "4" and "5", you must type:

By entering the first operant ("4") and pressing "ENTER", the operant is transferred from the input line to the first stack level.The second operant ("5") is entered in the input line and by pressing the calculation operation ("+"), it is added to the operant in the first stack level.

Through the calculation, the operants "4" and "5" are "consumed" by the calculation operation "+" and will disappear. Therefore, the result of the calculation ("9") is stored on the first stack level, instead.This is the basic concept of an RPN calculator. Operants are added to the stack and are used by calculation operations. The results of the calculation operations are again stored on the stack. For the calculation operations, always the lowermost values on the stack are used.

Depending on the kind of the calculation operation, one or two operants are needed. The "sin" operation for example needs one
operant, whereas operations like "+", "-", "*", "/" or "y^x" need two operants. If you try to perform a calculation operation with an insufficient amount of operants on the stack, a corresponding error message is displayed.

Managing the Stack

As stated before, the stack is an essential part of any RPN calculator. RPN Calculus has some unique features to handle the values on the stack. It is possible to delete single stack items or rearrange the items on the stack by touching and moving them.

To operate on a stack item, simply touch the item. The stack item gets highlighted and shows a delete and a reordering control:

Reordering
Control

Delete
Control

To delete the selected row, touch the delete control. To reorder the items on the stack, touch and hold the reordering control and drag the row to its new location. The stack will get reordered automatically. Of course, reordering the stack is only reasonable, if there is more than one item on the stack.

To clear all items on the stack at once, press the "AC" button.

To clear the lowermost stack item, you can also press the "C" button.

By pressing "Edit", you can edit the lowermost stack item. To do so, the stack value is transfered to the input line. The value can then be added to the stack again by pressing "ENTER".
If you press "Edit" while a stack item is seleced, the value of the selected stack row is transfered to the input line instead.

The "Lastx" button simply recalls the last value that was added to the stack in the input line again. This can be helpful to redo actions on the same value.

The "Swap" button swaps the position of the two lowermost values on the stack.
This could of course also be achieved by dragging the rows - however, pressing the "Swap" key is probably faster.

RPN Calculus can handle an unlimited amout of items on the stack. As you add more items to the stack, the stack gets expanded automatically. Also the stack shrinks, when items get deleted. You can scroll through the stack by touching and moving the stack table up and down.

Using the Memory

On the upper left of the RPN Calculus interface, you find the memory area. The memory can be used to store an unlimited amount of values and intermediate results during calculations. Any value on the stack can be added to the memory and every value in the memory can be copied to the stack - several times.

To add a value to the memory, first select the corresponding value on the stack by tapping on a stack row. When a stack row is selected, a small arrow-button, pointing towards the memory area, is displayed between the stack and the memory:

"add to memory"
button

By tapping on the arrow button, the value of the selected stack row is copied to the memory.

To recall a value in the memory to the stack, tap on a value in the memory table. The memory row is selected and a small arrow-button pointing towards the stack area is displayed between the stack and the memory:

"recall to stack"
button

By tapping on the arrow button, the value of the selected memory row is copied to the input line of the stack.

To delete single values from the memory, tap on the delete control displayed on the left side of the selected memory row. To delete all memory items, tap on the delete control shown in the header area of the memory table.

"delete all memory items" button

"delete memory value"
button

Scientific Constants

RPN Calculus has a build in constants dictionary. The dictionary contains over 120 scientific constants of different categories like e.g. Mathematics, Physics or Astronomy. Since the constants dictionary is user extendable, you can add constant values that you are maybe missing in the default set of constants.

You access the constants library by pressing the "Constants" button on the top left of the RPN Calculus Toolbar:

Constants Favorites

Frequently used constant values can be marked as "favorite" constants - for faster access. Constants marked as favorite show up in the "Favorites" list of the constants popover view. You can switch to the "Favorites" list using the segmentation control at the bottom of the "Categories" view. To mark a constant as "favorite", touch on the little star symbol at the right side of a constant value. The star gets highlighted to indicate that the constant value is a "favorite" constant value. Touch the star symbol again to remove a constant value from the "favorite" constants. Alternatively, you can choose "Edit" at the bottom of the "Favorites" list and delete constant values from the list. The constant will be removed from the "Favorites" list, but the constant value will remain in its category. To end the edit mode, choose "Done".

Edit Constants Categories

To edit the constants categories, touch "Edit" at the bottom of the "Categories" list view. In the edit mode, you can add new categories, rename, delete or reorder existing categories. To end the edit mode, touch "Done" at the bottom of the "Categories" list view.

Edit Constant Values

To edit the constants values of a category, touch "Edit" at the bottom of a "Constant Values" list view. In the edit mode, you can add new constant values, edit, delete or reorder existing constant values. To end the edit mode, touch "Done" at the bottom of the "Constant Values" list view.

Name

Symbol

Value

Unit

RPN Calculus Settings

To show the RPN Calculus settings popover, tap on the "Settings" button in the RPN Calculus toolbar. In the settings popover, you can customize the following parameters of RPN Calculus:

Display Digits
Controls the number of decimal places show in the stack and memory. Available range is 2-15.

Display always Exponent
When switched to "on", all values will be displayed in the exponential notation (e.g. 1.2345E+3 instead of 1234.5).

Persist Stack Values on Exit
When switched to "on", values on the stack will be preserved when the application quits.

Persist Memory Values on Exit
When switched to "on", values in the memory will be preserved when the application quits.

Use Radian on Startup
When switched to "on", RPN Calculus uses radians (Rad) for trigonometric calculations on startup, when switched to "off", degrees (Deg) is used.

Sounds
RPN Calculus can play discreet sounds to give a better UI feedback. A sound can playend when a key of the calculator keyboard is pressed, or when an error occures (like a "division by zero" error, for example).

Using the "Sounds"section of the settings, you can switch on/off the key-sound or error-sound and control the volume of the sounds.

Special Functions and Buttons

RPN Calculus contains some special functions and keyboard buttons that you might not be familiar with from other calculators.This chapter describes the these keys.

1. Shift (or. 2nd) key. Switches some keys to alternate functions.

2. Switches between radians (Rad) and degrees (Deg) calculation of the trigonometric functions (e.g. sin, cos, tan, ...).

The current setting (Rad/Deg) is shown in the white label on the top left of the RPN Calculus GUI.

3. The "Rand" key generates a random number in the range between 0.0 and 1.0.

4. The backspace key can be used to delete the last entered digit in the input line.

That's it. Have a lot of fun using RPN Calculus!