Repository files navigation

A simple four-function visual calculator, implemented in Haskell.

This calculator is capable of evaluating (and visualizing) arithmetic expressions such as "1+1" or "(1+2)*(3+4)".

It supports:

• natural numbers (of arbitrary size);
• addition, subtraction, multiplication, and division;
• sub-expressions nested within parentheses;
• unary negation.

Here's aweb-based demonstration built withGHCJS andReflex.

The implementation includes:

• Data structures for encoding arithmetic expressions as trees (seeCalculator.Types)
• Functions for parsing arithmetic expressions from textual input (seeCalculator.Parsing)
• Functions for pretty-printing arithmetic expressions (seeCalculator.Printing)
• Functions for evaluating arithmetic expressions (seeCalculator.Evaluation)
• A simple command-line interface (seeCalculator.CLI)
• A simple graphical user interface (seeCalculator.GUI)

Also included:

• A simple demonstration of using aGADT to restrict the shape of a tree-based data structure (theExp type).

This project supports both GHC and GHCJS.

The dependencies for GHC and GHCJS are slightly different.

On Debian-based systems, first install the following dependencies:

• libcairo-dev
• libghc-pango-dev
• libghc-gtk3-dev
• libwebkitgtk-3.0-dev

Then issue the following commands:

stack setupstack build

The command line interface is built with GHC.

To run it, issue the following command:

stack exec calculator-cli

The web interface is built with GHCJS.

First ensure that you have a recent version ofNodeJS installed. (Version 6.6.0 or later should work.)

Then run:

./build-web-gui.sh

If the build is successful, it will notify you of where you can find the build output. For example:

Open the following file with your web browser to view the graphical user interface:/path/to/haskell/calculator/.stack-work/install/x86_64-linux/lts-7.15/ghcjs-0.2.1.9007015_ghc-8.0.1/bin/calculator-gui.jsexe/index.html

Copy and paste the final line into your web browser to view the user interface.

The test suite is built with GHC.

To run the suite, issue the following command:

stack test

To load the calculator library into GHCI, issue the following command:

stack ghci