Unsure Calculator

Build Status - Cirrus

If you want to run the Unsure Calculator from source, this repository is for you. Otherwise, please go to filiph.github.io/unsure to learn more about the Unsure Calculator itself, and run it—for free—from your browser.

Web app

The web calculator is in example/. To run it from source (assuming you have the Dart SDK installed):

$ cd example/
$ pub get
$ webdev serve --release

Now, navigating to http://localhost:8080 will open the page. Changing code in the project will trigger a rebuild. The --release flag is important, because otherwise the web worker won't work.

To publish the example to filiph.github.io/unsure, do the following:

  1. Install peanut (only once): pub global activate peanut
  2. Go to the example directory: cd example
  3. Run peanut: peanut
  4. Push the newly updated gh-pages branch to github: git push origin --set-upstream gh-pages

Command line tool

You can run the command line version of the calculator by executing something like dart bin/unsure.dart "10 * 2~3" from the root of the repository. To get help, run dart bin/unsure.dart --help.

You can compile the tool to a binary executable by running dart2native bin/unsure.dart -o unsure. Then, call the binary like this:

$ ./unsure "10~20 * 42"

An animated gif of the binary in action

This compiled binary starts much faster than if you run the code through dart bin/unsure.dart "...".

Note that the command line tool defaults to 1 million iterations (compared to the 250K iterations of the web tool). That makes it a bit more precise (meaning that the results will be a tiny bit closer to the truth, and the histogram will be smoother). We can do this because Dart (compiled or not) runs a lot faster than JavaScript. That said, in my experiments, 250K iterations is precise enough.

Easy installation

If you don't want to clone the repository and just want to try the command line tool, you can use pub (part of the Dart SDK) to install it:

$ pub global activate unsure

Or, if you have the Flutter SDK installed:

$ flutter pub global activate unsure

You might need to follow instructions that pub gives you, but after that, you can just run unsure as a regular command line program from anywhere.


Apart from that online tool, this is also a (beginning of a) package. Read through bin/unsure.dart to see how it might be used.

Here's a more low-level example of use:

import 'package:unsure/unsure.dart';

void main() {
    var principal = 1000;
    var interestRate = Range(2, 4);
    var time = Range(10, 12);
    var calc = Calculation(
      () => principal * (1 + interestRate.next() / 100) * time.next());
    var result = calc.run();

In this example, we defined one constant (principal), two ranges (interestRate and time), and a custom callback that computes compound interest given the above. The callback can be arbitrary Dart code: you are not limited to the format understandable by lib/src/parser.dart.

Help needed

There's only so much I (Filip) can do myself. If this is ever going to be a truly open source project, I need to remove myself from a lot of the ownership of this thing.

  • Can you help me publish the CLI binary to popular repositories such as APT, Homebrew, or Nugget? I know how to compile the tool on each platform, but I don't know what to do next.
  • Can you come up with more interesting use case or formula, and write an article about it? The companion article at filiph.github.io/unsure is already too long.
  • Similarly, can you record a video tutorial explaining the use of this tool?
  • Can you help me automate the creation of binaries for each release, for each platform? I hear GitHub actions is the way to do it, but I've never done it.
  • If you're familiar with package:petitparser, can you help me rewrite the formula parser so it's more helpful? In particular, I'd like it to give more helpful feedback to the user.
  • Can you help me automate test coverage reporting?
  • Can you help me make the command line executable more stable?
  • Can you help me make the Unsure Calculator site into a true Progressive Web App?
  • Can you help me put the range (~) notation into more calculators out there?

If you're interested in helping, please see if there's an issue you might assign to yourself, and if not, create it.


I've done some research on what people generally mean when they say things like "certainly" in regular speech. This might be useful when talking about probabilities with untrained statisticians (such as myself).

Noun Adverb Percentage Sigma
All Certainly 100 % -
Almost all Almost certainly 95 % 2
Large majority Quite possibly 68 % 1
Bare majority Possibly 50+ % -


Support for doing uncertain computation.