cmp-rpncalc

nvim-cmp source for math calculations using Reverse Polish Notation

Installation

Use your favorite plugin manager to install this plugin. vim-pathogen, vim-plug, and Packer.nvim are some of the more popular ones. A lengthy discussion of these and other managers can be found on vi.stackexchange.com.

If you have no favorite, or want to manage your plugins without 3rd-party dependencies, use packages, as described in Greg Hurrell's excellent Youtube video: Vim screencast #75: Plugin managers

Setup

There is no setup required specifically for this plugin; however, you need to add rpncalc to the list of sources in your nvim-cmp setup. The following snippet shows how to do that.

require'cmp'.setup {
  sources = {
    { name = 'rpncalc' }
  }
}

How Does RPN Work?

RPN is a mathematical notation in which the operator follows its operand(s). This means there is no need for parentheses. Here are some examples, comparing algebraic notation to RPN.

Algebraic	RPN (this plugin's flavor)	Result
$956 + 37$	`956 37 +`	`993`
$\frac{452}{12}$	`452 12 /`	`37.666666666667`
$\tan^{-1}(\frac{1}{\sqrt{3}})$	`1 3 sqrt / atan deg` or `3 sqrt \ atan deg`	`30`
$3x^2+6x-5 \vert _{x=\frac{\sqrt{17}}{4}}$	`17 sqrt 4 / xm drop 3 rm 2 ** * 6 rm * + 5 -`	`4.3721584384265`
$e^{i\pi}$	`e i pi * **`	`-1+1.2246467991474e-16i` round off error 🙁

Reading an RPN expression from left to right, numbers are placed on a stack. The top four numbers are labeled X, Y, Z, and T from the top down. Although these labels are not shown when using the plugin, they are referenced in the README and the documentation. When an operator is encountered, one or more numbers (as needed by the operator) are popped from the stack, and the result of the operation is pushed back on the stack.

Complex Numbers

Most of the operators also will process complex numbers. The following Wikipedia pages were used as reference for some of the more arcane derivations for complex numbers. Where the complete answer is an infinte number of answers, only the principal value is given.

Operands

Operands can take on any of these forms:

Decimal - integer, floating point, scientific notation
Binary - 0b prefix, followed by digits 0 and 1.
Hexadecimal - 0x prefix, followed by digits 0-9 and letters a-f.
Complex - an ordered pair of numbers in any of the above formats. For example 1.2,-0x43 represents 1.2-67i.

Operators

The operator categories and certain exceptional functions show the types of numbers for which they are valid.

ℝ - real
ℕ - natural
ℂ - complex

Basic Arithmetic - ℝ and ℂ

+ - Addition
- - Subtraction
* - Multiplication
/ - Division
div - Integer division
% - Modulus (ℝ only)
abs - Absolute value
arg - The angle between X and the x-axis
chs - Negation

Powers & Logs - ℝ and ℂ

exp - Raise e to the X power
log - Natural Log of X
log10 - Log (base 10) of X
log2 - Log (base 2) of X
sqrt - Square Root
** - Raise Y to the X power
\ - Reciprocal

Trigonometry - ℝ and ℂ

Variations: a*** are inverse, and ***h are hyperbolic.

Sine - sin asin sinh asinh
Cosine - cos acos cosh acosh
Tangent - tan atan tanh atanh
Cosecant - csc acsc csch acsch
Secant - sec asec sech asech
Cotangent - cot acot coth acoth

Rounding - ℝ and ℂ

floor - Round down to nearest integer
ceil - Round up to nearest integer
round - Round to nearest integer
trunc - Truncate to integer

Bitwise - ℕ

These operators will truncate non-integer operands.

& - AND
| - OR
^ - XOR
~ - NOT
<< - Left Shift (Y shifted X places)
>> - Right Shift (Y shifted X places)

Constants - ℝ and ℂ

pi - 3.141592653...
e - 2.718281828...
phi - the golden ratio, 1.618033989...
i - 0+1i

Statistics - ℝ

! - Factorial
perm - Permutation of Y things taken X at a time
comb - Combination of Y things taken X at a time
mean - Average of all numbers on the stack (also ℂ)
std - Sample standard deviation of all numbers on the stack
sum - Sum of all numbers on the stack (also ℂ)
ssq - Sum of squares of all numbers on the stack (also ℂ)
count - Sample size

Memory and Stack Manipulation - ℝ and ℂ

xm - Store the value of X to memory
rm - Recall the value in memory and put it on the stack
m+ - Add X to the value in memory
m- - Subtract X from the value in memory
xy - Swap X and Y on the stack
x - Place the value of X from the last operation back on the stack
drop - Remove X from the stack

Miscellaneous - ℝ

hrs - Convert (Z hours:Y minutes:X seconds) to X hours
hms - Convert X hours to (Z hours:Y minutes:X seconds)
bin - Print results in binary (base 2).
hex - Print results in hexadecimal (base 16).
dec - Print results in decimal (base 10).

Disclaimer ⚠

The author of this plugin does not make any warranties about the completeness, reliability or accuracy of this calculator. Any action you take upon the results you get from it is strictly at your own risk. The author will not be liable for any losses and/or damages in connection with the use of this calculator.

Feedback 📣

This was mainly an exercise to learn lua and Neovim plugins by porting my prior Ruby and Erlang rpn calculators. It's quite possible that computational errors made their way in, despite all efforts to ensure its accuracy. If you spot any errors, or have suggestions for improvements, new operators, etc., create an issue or a pull request.

Finally, I don't know how useful some of the complex number functions are. It was a fun exercise implementing them, but was it just that, an exercise? Leave a comment (in an issue is fine) if you know of any real-world use (pun intended) for, let's say, the inverse hyperbolic cotangent of a complex number.

PhilRunninger / cmp-rpncalc