Clone repository and pip3 install ./rpncalc to install the calculator.

Calling rpncalc with no arguments will print a list of commands available to the calculator. A likely out of date example of the help page is below.

Reverse Polish Calculator on input argument strings.  An example `rpncalc 1 2 +`
  should push 3 to the stack.  The available operators are:
 BinaryOperators:
  +, -, *, /, //, ^, atan2, log_base, =, >, >=, <, <=, choose, combo, %, divmod
 UnaryOperators:
  sin, cos, tan, acos, asin, atan, int, exp, expmxsq, !, ln, log10, sqrt, 1/x,
  uminus
 IdempotentOperators:
  print, print_sv, print_store, print_state, quit, exit
 ReductionOperators:
  sum, prod, mean, max, min, stdev, sem, var
 LinearAlgebraOperators:
  vec2, vec3, veca, vecn, dot, cross, mat2, mat3, matsq, matmn, det, inv, T,
  e_x, e_y, e_z, hstack, vstack, reshape, normalize, norm, to_stack
 Constants:
  true, false, pi, tau, e, c, h, mu0, Na, kb, R, G, g, m_e, m_p, m_n
 StateOperators:
  clear, clear_storage, swap2, reverse, pop, save, load, repeatn
 RandomOperators:
  rand, coin, normal, d2, d4, d6, d8, d10, d12, d20, d100
 HistoryOperators:
  history, get_history

Use help(cmd) or help_cmd for detailed help on specific operators such as
  help_matsq

Flags:
 --verbose, -v. Print how the stack is processed
 --interactive, -i. Launch interactive input loop
 --load, -l.  Load from specified snapshot file
 --debug. Set breakpoints after expression evalution

Be wary that many commands involving certain characters must be encapsulated in quotes or your shell will expand them before passing them to the script. Launching the script with -iv for interactive mode can be less hassle.

Incomplete commands will return the contents of the stack, such as rpncalc 2 2 2 + will return [2, 4].

Items can also be stored as named constants by prefixing the desired name with store_, to be retrieved by prefixing an _ later. These variables are stored in a dictionary and can be accessed until overwritten. A usage example calculating the vapor pressure of ethanol via Antoine's equation (A 3-parameter fit of 10^(A-B/(C+T)) at T=78.32C is given below. Units for the fit coefficients are most not SI, and give ye olde mmHg.

rpncalc -v 8.2042 store_A 1642.9 store_B 230.30 store_C 10 _A _B _C 78.32 + / - ^ gives output:

Stack: [8.2042]
Popping stack into stored value _A
Stack: [1642.9]
Popping stack into stored value _B
Stack: [230.3]
Popping stack into stored value _C
Stack: [10]
Pushing stored value _A to stack
Stack: [10, 8.2042]
Pushing stored value _B to stack
Stack: [10, 8.2042, 1642.9]
Pushing stored value _C to stack
Stack: [10, 8.2042, 1642.9, 230.3, 78.32]
Applying BinaryOperator.addition
Stack: [10, 8.2042, 1642.9, 308.62]
Applying BinaryOperator.division
Stack: [10, 8.2042, 5.323375024301731]
Applying BinaryOperator.subtraction
Stack: [10, 2.8808249756982693]
Applying BinaryOperator.power
Stack: [760.0199208394923]

Example below is linear regression fitting y=2+x via inputting x,y datapoints and creating the Vandermonde matrix V, and solving for the coefficients of fit via a=(V^TV)^-1V^Ty. This construction fits linear coefficients to the functions are applied in the columns of the matrix, in this case 0th and 1st degree terms of x for a line, but coefficients can be fit for any f(x).

rpncalc 0 1 2 3 4 veca store_x 2 3 4 5 6 veca store_y _x 0 ^ _x 1 ^ hstack store_V _V T _V dot inv _V T dot _y dot gives the intercept and slope as:

Stack: [array([[2.],
       [1.]])]

This was built as an experiment of using python emums with match statements for python3.10. Input strings are cast to callable enum classes, and then processed via a stack. Perhaps not wholly wise to implement an RPN calculator using these tools (see the __new__ override in the ActionEnum class), as well as the potentially overcomplicated creation of the cli help. Adding a bash-like history and interactive modes for the calculator were surprisingly simple.