Entry for the Delegate code competition

This is my entry for the Delegate code competition. The source language chosen for this implementation is Haskell due to the similarities between the host- and target language as well as the availability of 'beautiful' parser combinators. The Glasgow Haskell Compiler is required to run and test the parser as well as the AST (http://www.haskell.org/ghc/).

Files:

1. DelegateAst.hs - Defines the abstract syntax tree for the Delegate DSL as well as Read and Show instances.
2. DelegateParser.hs - Defines the parser for parsing the delegate DSL into the AST. To parse a string or the contents of a file into the AST, import the module and invoke either parseString :: String -> Either Error Order or parseFile :: FilePath -> IO (Either Error Order) repectively.
3. DelegateTest.hs - Tests of the parser, Show and Read instances. See the file for details.

Compatibility:

The code conforms to the specifications of the assignment. The code block:

order { add “Raspberry Pi” 34 Units At 41 If OutOfStock Wait 16 Months
        add “Mad Catz M.O.U.S.9” 55 Units At 43 If OutOfStock Wait 32 Weeks
        add “The Riftshadow Roamer” 89 Units At 47 If OutOfStock Wait 64 Days }

Compiles into an AST whose Show-instance prints it as a list separated by semi-colons, as required by the assignment:

Order[OrderLine(Product(“Raspberry Pi”,34),Price 41,Period(16,Months));
      OrderLine(Product(“Mad Catz M.O.U.S.9”,55),Price 43,Period(32,Weeks));
      OrderLine(Product(“The Riftshadow Roamer”,89),Price 47,Period(64,Days))]

Furthermore, the implementation allows reading the above input as a semicolon-separated list as well (i.e. both code blocks compile into the AST, and the Read and Show instances form a bijection between the AST and the string-representation of the AST, here represented by the second code part. That is, for a Delegate AST, x :: a, Read(Show x) :: a == x).

Drawbacks/future improvements:

• Printing of ASTs could be prettier; there is no indentation or newlines.
• Due to the parser library used, arbitraryly nested parenthesizations of OrderLines are not supported (this was not a requirement, however it might be desirable).