Ruby is an awesome programming language. Its metaprogramming capabilities make it easy to turn the interactive ruby interpreter (irb) into an awesome desktop calculator. To do so, we can make irb execute a ruby script, containing some calculator extensions before it starts, with the following command:

irb -r /path/to/the/file.rb

Of course, you will want to make an alias or keyboard shortcut for this. In bash, this can be done by adding something like the following to ~/.bashrc:

alias rcalc='irb -r /path/to/the/file.rb'

Here's a link to my custom ruby calculator script. Here's what it does:

+----------------------------- RUBY CALCULATOR -------------------------------+
|  0b - Binary    .b - To Binary      Constants: E, PI                        |
|  0x - Hex       .h - To Hex         _ gives last result                     |
|  0  - Octal     .o - To Octal       q quits                                 |
+-----------------------------------------------------------------------------+
|  Window closes after 10 minutes of inactivity. Type 'keepalive' to disable. |
+-----------------------------------------------------------------------------+
irb(main):001:0> 0b11111111
=> 255
irb(main):002:0> _.h
=> "ff"
irb(main):003:0> PI
=> 3.14159265358979
irb(main):004:0> E
=> 2.71828182845905
irb(main):005:0> 2**256 / 3**5
WARNING: Integer division with remainder.
=> 476510655297597512031156316908180690754197467759837712096533267522276253662
irb(main):006:0> 6/3
=> 2
irb(main):007:0> 5.0/2
=> 2.5
irb(main):012:0> sin(PI/2)
=> 1.0
irb(main):008:0>

I will be adding functionality to this script as I need it. Some things I'm planning are:

• Unit conversions
• Easier way to convert strings in different bases to integers
• Efficient factorial function
• Common sequences such as Fibonacci
• Common formulas
• Common constants (c, G, etc.)

If you have any ideas, please leave a comment and I'll add it to the list.