SpicyRPN is a Reverse Polish Notation (RPN) calculator that runs on any Apple iOS 7.0 or later device. It includes a wide variety of scientific and business functions. Launching in 2016!

SpicyRPN shown on iPhone 6

What is special about SpicyRPN?

SpicyRPN was designed from the ground up based on the author’s 30 years of experience using RPN calculators in engineering and business settings. It solves some of the problems you will find in typical RPN implementations. Here are a few specifics:

  • 38 digits internal precision. Improving precision of long chains of calculation.
  • Adaptive digits display.  Taking maximum benefit of the devices’s size and orientation.
  • 5 Position RPN stack. For that little bit of extra headroom for complex calculations.
  • Advanced Scientific & Business Functions. Including some rare ones.
  • Sliding Button Panels. So all functions are always available, even on smaller devices.
  • All iOS 7.0 and later devices, all orientations. This is a universal app for any iOS device.

Why RPN?

Reverse Polish Notation is an entry system in which the operands are entered first, followed by the operators. For example, you enter 3 4 + rather than 3 + 4 = to calculate the sum of 3 and 4. There are no parentheses in RPN since they are not needed. RPN has several advantages over algebraic entry systems:

  • No need for operator precedence
  • No need for parentheses
  • Fewer keystrokes needed for calculations
  • Easier to keep track of complex calculations

Its only disadvantage is that it takes some effort to learn the system, and some practice to become proficient. But RPN, once the skill is acquired, has been proven in studies[1][2] to be faster and result in fewer errors.

Algebraic and RPN Entry Examples

Functions available on SpicyRPN

The Basic Key Group

Basic Key Group

  • Standard RPN controls: Enter, Rotate stack, Swap, LastX
  • Digit entry with exponents and backspace, and clear
  • Entry modification: ABS, INT, FRAC, RND, +/-, etc.
  • Exponent display: FSE (Fixed/Scientific/Engineering)
  • Decimal position: FIX (from 0 to 38 digits)
  • Angle mode options: DEG (Degrees/Radians/Gons)
  • Four-function operators: Add, Subtract, Multiply, Divide
  • Constants: π and e stored with precision of 38 digits
  • Random number generator, uniform distribution [0,1)
  • Percentage operations
  • Memory operations, standard & associative
  • Square, square root, reciprocal functions
  • Function shift key for shifted operations
  • On board help system (does not require Internet)
Scientific & Statistics Key Group

Scientific and Statistics Key Group

  • Standard exponent and log functions
  • Factorial and Gamma function
  • Error function and its complement
  • Trigonometric functions and inverses
  • Hyperbolic functions and inverses
  • Combinations and permuations
  • Accumulating statistics entry (1- or 2-variable)
  • Standard deviation, mean & weighted mean
  • Linear estimate & correlation coefficient
  • Linear regression
Financial functions key group

Financial Key Group

  • Compound interest entry and calculation for any of period, interest rate, present value, payment, future value
  • Generalized cash flow entry, display and computations
  • Net present value, internal rate of return for cash flows
  • Date calculations and days between date
  • Loan Amortization
  • Bond price & yield
  • Depreciation calculations