DATX02-DIT561

Daison Frontend

This project is the result of a Bachelor's thesis in Computer science and engineering (DATX02 / DIT561), given at Chalmers University of Technology and University of Gothenborg.

The purpose of the project is to study how the compiler GHC can be used as a library to build a front-end for Daison. The project focuses in particular on how GHC as a library can be used to build interactive Haskell environments.

Project structure

• Setup.hs - Default setup for building executables.

• src/ - Haskell sourcecode

  • Main.hs - Start the program
  • Frontend/ - Contains the Haskell sourcecode.
    • Base.hs - Session/State handling
    • Context.hs - Extensions/Flag handling
    • Eval.hs - Evaluate expressions sent through the CLI
    • Format.hs - Format output from Daison queries
    • GHCInterface.hs - No own implementations here, purely for imports.
    • Run.hs - Loop of the program and definitions of commands that can be run
    • Typecheck.hs - Typecheck user input to decide how to handle it.

• tests/ - Contains automated tests for the program

  • Tests.hs - Functional tests run with QuickCheck
  • UnitTests.hs - Unit tests run with HUnit

Running the application

We used Cabal to automate dependency installations, building as well as testing the project. Run the following commands from the source folder:

Run:

cabal run daison-frontend

Test:

cabal test

Build executable

cabal build exe:daison-frontend

Get a simple binary in the folder dist/

cabal install exe:daison-frontend --install-method=copy --overwrite-policy=always --installdir=dist

Example usage

1. Start the program

~$ daison-frontend

2. Open a database

:open database.db

3. Load a local file with table and type definitions (people :: Table Person, Person :: Person { name :: String, age :: Int})

:load People.hs

4. Create a table which is defined in People.hs

tryCreateTable people

5. Read all entries in the people table

select [x | x <- from people everything]

6. Insert a new person into the table people

insert people $ return $ Person "Alice" 15

7. Update her age

let pkey = fst it
update people [(pkey, person{age=25}) | person <- from people (at pkey)]

8. Close the program

:quit

Available commands

Command	Description
<statement>	evaluate/run <statement>
:dbs	print the list of databases that are currently open
:?, :help	display this list of commands
:log path	display the log file's path
:log show	display the log file's contents
:log toggle	enable/disable logging
:log wipe	attempt to wipe the log file's contents
:type <expr>	show the type of <expr>
:q, :quit	quit the program
:! <command>	run the shell command <command>
:close <name>	close database with <name> if opened
:mode [mode]	set access mode to [mode] if provided; displays the current access mode otherwise
:open <name>	open database with <name> or set focus to <name> if already opened
:cd <dir>	set the current directory to <dir> (relative to current location)
:module <module>	import <module> if it exists and is in scope
:load <filepath>	load a haskell file from <filepath>
:set <option>	set GHC <option>

Authors

Name	GitHub-handle
Christoffer Kaltenbrunner	kaltenbrunner
Alexander Neldefors	PUGzera
Hugo Stegrell	steget
Philip Vedin	pvedin