Dicey on the Web

What's this?

This is an online version of Dicey: a dice distribution calculator and roller.

See it in action at dicey.bulancov.tech!

It has these amazing, never-before-seen features:

• support for custom dice: any numbers will do!
• support for textual dice: who needs numbers when you can use words?
• fast¹ calculation of probabilities for each possible roll
• meaningful addition of text and numbers
• works well in major browsers, with desktop and mobile layouts and light/dark themes
• can be used offline or installed as a web app
• will probably hang your browser tab

¹ fastness not guaranteed, depends on number of distinct rolls

How's it work?

There are several components to this app:

• a Ruby interpreter WASM module that allows running Ruby code in the browser
• Dicey, the underlying Ruby gem that does the calculations
• VectorNumber, another Ruby gem that handles mathematical operations on mixed text and numbers
• a gluing script (in Ruby again) that handles UI
• and a service worker to infest your computer with all of the above

There are also my awesome CSS, HTML and SVG skills that created the UI.

What's the custom dice syntax?

Informally, following forms are allowed:

• N — a regular die with N faces
• N..M — a die with faces from N to M
  • Accepts negative integers
• A,B,C,D — a die with faces A, B, C, D
  • Accepts fractions in decimal-dotted and vulgar forms: 1.5, 3/2
  • Accepts arbitrary text
• Any form above can be prefixed with Nd to add N dice

Why's this?

I was very dissatisfied with dice calculators I could find as they were just glorified combinatorics calculators with unneeded explanations and convoluted UIs. Maybe there are actually good ones? I dunno, I could only find teaching aids and "roll around and find out" thingies.

So I created Dicey as a personal project to actually get useful data all at once: a full table with all results, and no unneeded garbage. And then it kept expanding. At one point I decided to create VectorNumber, as more esoteric dice can have non-numeric faces, and we need to be able to meaningfully add everything together (though integrating it took a long while, whew!).

I was talking to a friend one day about this project and the possibility of spreading it other people, and they said "If your program is hard for users to access or install, it's shit." I was understandably miffed, but they were right: a CLI app written in Ruby is not exactly user-friendly. Most people dealing with dice probably wouldn't even understand how to download it!

At some point I learned about the WebAssembly Ruby port and a lightbulb went off in my head: why not just run the actual Dicey code in the browser? And off I went to see the wizard to create this online version.