A utility for displaying a truth table for an expression
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README.md

README.md

Truth::Table

A simple, thrown-together library for displaying a truth table for boolean expressions.

Usage

You can use the provided command-line tool to display an arbitrary expression:

$ truth "A && B || C"
Expression:
A && B || C

 A  B  C | =
---------+---
 f  f  f | f
 t  f  f | f
 f  t  f | f
 t  t  f | t
 f  f  t | t
 t  f  t | t
 f  t  t | t
 t  t  t | t

Or, you can do it programmatically:

require 'truth'

table = Truth::Table.new("A && B || C")
table.display

You can also generate Karnaugh maps (K-maps). From the command-line, just pass -k to the truth tool to have it display both the truth table and the K-map:

$ truth -k "A && B || C"
Expression:
A && B || C

 A  B  C | =
---------+---
 f  f  f | f
 t  f  f | f
 f  t  f | f
 t  t  f | t
 f  f  t | t
 t  f  t | t
 f  t  t | t
 t  t  t | t

     AB
     00 01 11 10
    +--+--+--+--+
C 0 |0 |0 |1 |0 |
    +--+--+--+--+
  1 |1 |1 |1 |1 |
    +--+--+--+--+

Or, programmatically:

require 'truth'

table = Truth::Table.new("A && B || C")
table.kmap.display

Supported Operations

The parser is simplistic, but supports the following boolean operations:

  • NOT: !A
  • AND: A && B
  • OR: A || B
  • XOR: A ^^ B

The || and ^^ operators have the same precedence, with && being higher than either, and ! being highest of all.

Parentheses may be used to group expressions.

Caveats

This was thrown together as a proof of concept, and is being made public primarily because I spent time on it and figured it might help someone else. There are not currently any tests (shame on me!) but I would gladly accept a pull request if someone is feeling ambitious.

License

This code is written by Jamis Buck jamis@jamisbuck.org and is distributed under the MIT license (see the MIT-LICENSE file).