Foul EDITor

CS410 Final Assignment

Darren Mowat

200911909

Things added to the FOUL Language

• Rewrote the parser using Parsec. It now output useful error messages & positions to help find errors
• Rewrote the interpreter to handle errors more gracefully
• Check the program before interpreting for duplicate method declarations and functions declarations that take different numbers of parameters
• Added single line comments to the language (-- Comment Goes Here)
• Added a module import system to the parser. Users can define their own functions in separate files and import them in.
• Implemented some standard library modules. These modules are not part of the interpreter, they're foul files stored in the std directory of this repository. Cabals Path_fedit module is used to access them on the host system at runtime.
  • import std/math: Add, Subtract, Multiply, Divide, Equals, More Than, More Than Equals, Less Than, Less Than Equals, Square, Fibonacci & Infinity (Negative numbers aren't supported and causes a crash)
  • import std/bool: Conditional Application (cond), and, or & not
  • import std/test: Module used for testing. Its used to implement tests for std/bool & std/math (tests are in tests/FOUL)
• Add basic integer support to the parser. Instead of writing S(S(S(Z))) you can just write 3 (both in patterns and expressions)
• Pretty Print Values (VC "T" [] -> T, VC "S" [VC "Z" []] -> 1)

Things added to the editor

• Fixed handleKey bug which loops forever and uses 100% CPU
• Evaluate the main function of the file on exit
• Save the file on exit
• Line Numbers
• Added a way to evaluate expressions within the files. This is available using the following syntax
  • -- eval EXPR
  • -- eval add(7, 8)
  • The answer will then be inserted into the comment -- eval add(7, 8) -> 15
  • Evaluation is triggered by typing Ctrl+e
• Display parser errors at the bottom of the editor window
• In line evaluation errors as comments

Installation

FOUL & Fedit are packed using Cabal as they have some external dependencies that would be hard to manage with MakeFiles. Cabal will build 2 seperate binarys when run

* foul - FOUL parser and evaluator
* fedit - Foul EDITor 

Get a copy of this repository either by

git clone https://github.com/DarrenMowat/fedit.git

Or by downloading it as a zip file from https://github.com/DarrenMowat/fedit/archive/master.zip

cd fedit
cabal configure
cabal install

The fedit & foul binaries should now be available on your PATH somewhere

Sample FOUL Files

There is a modified implementation of the sorting function in sample/mysort.foul. It utilises the standard library modules, comments and the use of integers as expressions.

There are also some test files designed to test the standard library functions in tests/FOUL/*.

The standard library modules are defined in std/*. These show an example of using integers as pattern variables

Screenshots

• Parse Error

• Evaluating fib(20)

• Maths standard library