bcalc

A calculator written in pure bash.

I even managed to write a lexer and parser for the argument input,
allowing you to do 1+1 instead of 1 + 1.

I made sure to thouroughly comment the script,
feel free to check it out if you're interested!

Syntax

• () = do this first and replace with the done math
• ^ = exponent
• * = multiplication
• % = division with remainder
• / = division
• + = addition
• - = subtraction

What's supported

• Basic math operations
• PEMDAS
• Whole numbers

Examples:

$ ./bcalc 100*50
5000

$ ./bcalc 1000/100
10

$ ./bcalc 100+100+100+100
400

$ ./bcalc 9-1-2-3-4
-1

$ ./bcalc '(100+50)/2'
75

$ ./bcalc '(100+50)+2^2'
154

There is also a debug mode implemented,
which is useful for when the output seems wrong.

Here is an example:

$ ./bcalc '(100+100-100)+100' --debug
final_array = ( 1 0 0 + 1 0 0 - 1 0 0 ) + 1 0 0
ip_split = 100+100 100
ip_split[0] = 100+100
first = 200
ip_split[1] = 100
second = 100
ip = 100
mn = 1 0 0
numbers = 100
number_array[0] = 100
operation_array[0] = +
operation_array[1] =
number_array[1] = 100
operation_array[0] = +
operation_array[1] =
number_array[2] =
operation_array[0] = +
operation_array[1] =
number_count = 2
operation_count = 1
calculation = 100+100
200

• final_array = the complete array of characters that were inputted
• ip_split = if what's in parenthesis contains a -, split based on that into an array
• first = the first calculation to be done before the subtraction (first - second)
• second = the second calculation to be done before the subtraction
• ip = anything in this array is what is inside parenthesis
• mn = short for multi-digit number
• number_array = an array of all the numbers
• operation_array = an array of all the operations
• calculation = the calculation to be used

Testing

There is a script provided (test),
which will test the calculator to make sure it's functioning properly.

Example output:

$ ./test
GOOD -- The basic parenthesis test has passed.
GOOD -- The basic exponent test has passed.
GOOD -- The basic multiplication test has passed.
GOOD -- The basic division test has passed.
GOOD -- The basic addition test has passed.
GOOD -- The basic subtraction test has passed.
GOOD -- The basic PEMDAS test has passed.
GOOD -- The second basic PEMDAS test has passed.
GOOD -- The error test for notations passed.

If a test fails, it will display the result and what was expected.
It will also output a respective debug file for the test to debug/.

TODO

• Better formatted ouput (perhaps 1,000,000 instead of 1000000 for example)
• No hard limit on number/operator count
• Support decimals apparently this is not possible in pure bash
• Support PEMDAS (bash had already mostly supported PEMDAS, just needed to support for parenthesis)
  • Parenthesis
  • Exponents
  • Multiplication
  • Division
  • Addition
  • Subtraction

Off-topic from this calculator:

I feel like the work I would put into the lexer for this calculator,
can be adapted into a framework for creating custom languages in BASH.

I'm definitely going to look into this after I've done more work on the calculator.