stefankoegel / clickyEvaluation

Visual tool for stepwise evaluation of simple Haskell expressions

Clicky Evaluation

Description

Clicky Evaluation parses simple Haskell-like expressions and function definitions and renders them as HTML. The user can then choose which subexpressions to evaluate for one step by clicking on them. This is intended as a simple learning tool for beginners, which shows them how their Haskell code might be evaluated.

You can try it here.

The projects name is a play on lazy evaluation and clicking to evaluate an expression.

Supported Features

• Bool
• Char
• Int
• String
• List
• Tupel
• Arithmetic operators [(+), (-), (*), ('div'), ('mod'), (^)]
• Comparsion operators [(==), (/=), (<=), (<), (>), (>=)]
• Boolean operators [(&&), (||), (not)]
• Other operators [($), (.), (:), (++)]
• Infix to prefix conversion a + b <=> (+) a b
• Pattern matching on atoms (numbers, ...), lists and tuples
• Anonymous functions (lambdas)
• Sections (^2) 4 => 4^2 => 16
• Most of the simple Prelude functions on lists head, map, foldr, scanr, filter, all, ...
• Types for Bool, Char, Int, List, Tupel and Prelude functions
• Type inference for user defined functions and expressions
• ADTs
• Listcomprehensions

Missing Features

• Guards
• case, where, let
• Multi-line expressions, significant whitespace
• Floating point numbers
• Comments
• Type classes

Building

Install npm and purescript (at least 0.8.0). You can get purescript via cabal install purescript or npm install purescript. Then run:

npm install
npm run build

For the unit tests you can also run:

npm run test

After a successful build use:

<your_browser> html/index.html

Hosting

You can build and host a specific version of ClickyEvaluation yourself by providing the following files on your webserver:

• index.html
• source.css
• Main.js (generated with npm run test or pulp build --to Main.js)

Or you can link to the most recent version here.