rpnCalc is a simple, reverse-polish notation calculator licensed under the MIT license written in C. It supports the following features:

* Basic arithmetic
* Exponents, roots, and logarithms
* Trigonometric functions in radians, degrees, and radians
* Factorial, choose, permutations
* 1-variable statistics calculations (mean, sum, product, variance, standard deviation)

Building
--------

Building rpnCalc is as simple as running 'make' and 'make install'.

Running
-------

rpnCalc can be started by executing the command 'rpncalc' after building and installation.

User's Guide
------------

rpnCalc is an interactive calculator. After it starts up, you are greeting with a prompt (>). You should enter commands at this prompt to be evaluated

> 4 3 +
7.000000
> 7 *
49.000000
> 

After each line is executed, the item at the top of the stack is displayed. There are a few exceptions to this, which are explained in more detail below.

Arithmetic
----------

+ - Addition
- - Subtraction
/ - Division
* - Multiplication

> 3 4 *
12.000000
> 3 /
4.000000
> 2 -
2.000000
> 1 +
3.000000

Exponents, Roots, and Logarithms
--------------------------------

^ - Raise to power
rt - nth root
sq - square root
log - base 10 logarithm
log2 - base 2 logarithm
ln - natural logarithm

> 2 3 ^
8.000000
> 27 3 rt
3.000000
> 64 sq
8.000000
> 1000 log
3.000000
> 1024 log2
10.000000
> e ln
1.000000

Trigonometric Functions
-----------------------

sin - sine
cos - cosine
tan - tangent
tmode - changes degree measure used (default is radians)

> pi 4 / sin
0.707107
> deg tmode
> 90 sin
1.000000
> grad tmode
> 100 cos
-0.000000

Factorial, Choose, and Permutations
-----------------------------------

! - factorial
ncr - choose
npr - permutation

> 7 !
5040.000000
> 10 3 ncr
120.000000
> 10 3 npr
720.000000

Stack Manipulations
-------------------

inspect - list the contents of the stack
pop - pop item off the stack
clear - clear the stack

> 1 3 5 9
9.000000
> inspect
1: 9.000000
2: 5.000000
3: 3.000000
4: 1.000000
> pop
5.000000
> inspect
1: 5.000000
2: 3.000000
3: 1.000000
> clear
Stack cleared.
> inspect
Stack is empty.
> 

Miscellaneous Commands
----------------------

: - print item at top of stack
; - print item at top of stack, and then pop it

> 3 4 + : 7 *
7.000000
49.000000
> ;
49.000000
> inspect
Stack is empty.
>

Statistics Calculations
-----------------------

In order to perform statistical calculations, you must push numbers onto the 'stat stack.' This can be done using the spush or spushm commands. You can list the contents of the stat stack with the sinspect command.

spush
-----

The spush command pushes one item from the stack to the stat stack.

> 3 spush
> sinspect
1: 3.000000

spushm
------

The spushm pushes multiple items from the stack onto the stat stack. The first number popped off the stack tells the spushm command how many items to push to the stat stack.

> 1 3 4 5
5.000000
> inspect
1: 5.000000
2: 4.000000
3: 3.000000
4: 1.000000
> 4 spushm   
> inspect
Stack is empty.
> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> 

You can manipulate data on the stat stack in the same way you can on the normal stack. The spop command pops one number off of the stat stack, and the sclear command clears the stat stack.

After you have the data you want pushed to the stat stack, you can perform statistical calculations.

mean
----

The mean command gets the arithmetic mean of the numbers in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> mean
3.250000

sum
---

The sum command gets the sum of the numbers in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> sum
13.000000

sumsq
-----

The sumsq command gets the sum of each number squared in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> sumsq
51.000000

prod
----

The prod command gets the product of each number squared in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> prod
60.000000

vrnce
-----

The vrnce command gets the population variance of the numbers in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> vrnce
2.187500

svrnce
------

The svrnce command gets the sample variance of the numbers in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> svrnce
2.916667

stddev
------

The stddev command gets the population standard deviation of the numbers in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> stddev
1.479020

sstddev
-------

The sstddev command gets the sample standard deviation of the numbers in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> sstddev
1.707825

sn
--

The sn command gets the number of numbers in the stat stack.

> sinspect
1: 1.000000
2: 3.000000
3: 4.000000
4: 5.000000
> sn
4.000000