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A simple way to evaluate Boolean Algebra.

Project description

Caesium

License Code style: black Build Status

Caesium is a simple language built to help myself (and others) learn about and understand how Boolean algebra works. To this end, it can evaluate some

Installation

  1. Ensure that you have a working version of python (You can get python3 from the official site if you don't have it or want to upgrade). Any python version >= 3.4.0 should work.
  2. Install caesium using pip by running pip install caesium-lang from the command line.
  3. Test it out by running the command caesium in your command line.

Usage

Starting the Prompt

You can start the prompt by running caesium.

Example:

$ caesium
caesium v1.2.0 running on win32.
Press Ctrl+C or type "exit" to quit.
Cs>

If you want to close the interpreter now, skip down here to learn how to do that.

Expressions

An expression is any valid code which returns a value. In Caesium's case, that means that all valid code since all valid code must be an expression. Expressions are evaluated right to left unless brackets (()) are used.

Values

There are only 2 built-in values: True (or 1) and False (or 0). Caesium is case-insensitive so it will accept them in upper, lower and even mixed case.

There is also the random keyword which randomly evaluates to either True or False whenever it's used.

Cs> TRUE
True
Cs> False
False
Cs> tRuE
True
Cs> 0
True
Cs> 1
False
Cs> random
True

Assignment

You can assign a name to a value by putting a valid identifier on the left, then a = and any valid expression. A valid identifier is any string of Unicode text that is neither a keyword nor does it contain whitespace. Assignments can be chained together to define more than one variable at once. Since assignments are expressions, they can be nested within larger expressions.

Cs> foo = True
True
Cs> quux = coco = (True ^ (bar = True)) & False
False

Operators

In caesium (and Boolean algebra in general),there are 2 types of operators, basic operators and derived operators.

Basic Operators

Basic operators, together with the 2 Boolean values, are the building blocks of Boolean algebra. There are only 3 basic operators:

1. NOT

NOT takes one value and flips its value. NOT can also be written as !. Its operations can be summarised as:

Expression Result
NOT True False
NOT False True
2. AND

AND takes 2 arguments and checks if both of them evaluate to True. If they both do, it returns True, otherwise it returns False. AND can also be written as & or &&. AND operations can be summarised as:

Expression Result
True AND True True
True AND False False
False AND True False
False AND False False
3. OR

OR also takes 2 arguments and checks if both of them evaluate to False. If they both do, it returns False, otherwise it returns True. OR can also be written as | or ||. OR operations can be summarised as:

Expression Result
True OR True True
True OR False True
False OR True True
False OR False False

Derived Operators

Derived operators are called "derived" because they are derived from the basic operators (i.e: they can be re-written as basic operators). As programmers however, we are too lazy to write them out in full, so we made them as a kind of shorthand.

1. XOR

XOR, or eXclusive OR, works just like OR, but where both values cannot be True. XOR can also be written as ^. XOR operations can be represented in a table as:

Expression Result
True XOR True False
True XOR False True
False XOR True True
False XOR False False
2. NOR

NOR, or Not OR, also works just like OR, but it negates what OR returns. It can also be written as ~.NANDNOR operations can be represented in a table as:

Expression Result
True NOR True False
True NOR False False
False NOR True False
False NOR False True
3. NAND

NAND, or Not AND, works exactly like AND, but it negates what AND returns. It can also be written as @. NAND operations can be represented in a table as:

Expression Result
True NAND True False
True NAND False True
False NAND True True
False NAND False True

Comments

Comments are lines of text meant for other people to read, rather than for the interpreter to run. If a line begins with a # character, the entire line is treated by the interpreter as if it is blank.

Errors

When you try to run code which has a mistake (like a missing bracket), the interpreter complains about your code instead of running it. This is an error. An error is basically the interpreter alerting you that there was something wrong with the code and so it can't run it. Once an error is thrown, you will have to fix whatever is wrong with your expression and rerun it.

Examples:

Cs> quux
Undefined name "quux".
Cs> random/  # Meant to say "random"
Invalid syntax: "/".

Exiting

Either pressing Control + C or typing in exit and hitting Enter will cause the interpreter to stop instantly and take you back to the normal shell.

Cs> exit
$

TODO

  • An internal help mechanism so that you don't have to keep referring to the README.

Development Setup

  1. Inside of a fresh virtualenv, install development packages by running pip install -r requirements-dev.txt.
  2. Assert everything is working by running pytest tests.py from the project's root dir.

Contributing

  1. Crete your feature branch by forking the develop branch.
  2. Commit your changes.
  3. Push to origin/develop.
  4. Open a pull request.

Notes

Just like the element Caesium, this app may break down. In case it does, please contact me or if you want to, fix it yourself.

Meta

This project is licensed under the BSD 3-Clause License. Please see the license file for more information.

Project details


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