parskell

An embeded DSL in Haskell inspired by the game Human Resource Machine. Write a DSL with a limited amount of instructions that takes an input list and produces an output list.

The EDSL is made using Syntactic and the paper A Generic Abstract Syntax Model for Embedded Languages.

instructions

To run the DSL you'll need stack. The Levels are located in the src/Levels folder. Start with Level1.hs and read the top comment. To test your result run stack run <x> where you replace <x> with the level. The solutions can be found in the src/Solutions folder.

operators

To explain the different operators we'll use x, y, z,... to denote the parameters and (x::Type) to denote the Type the expressions evaluates to. When the Type is generic we'll use a, b,... . When a Haskell literal is expected we'll use n e.g. 1, True,...

numerical

• num n :: Int
  represents a literal of type Int where n is the value e.g. 2
• (x::Int) + (y::Int) :: Int
  adds x and y together
• (x::Int) - (y::Int) :: Int
  subtracts y from x
• (x::Int) * (y::Int) :: Int
  multiplies x and y together
• (x::Int) ** (y::Int) :: Int
  raises a to the power of b

Logic

• (bool n) :: Bool
  represents a literal of type Bool where n is the value e.g. True
• not (x:Bool) :: Bool
  negates the boolean x
• (x::Int) == (y::Int) :: Bool
  returns whether or not x is equal to y
• (x::Int) < (y::Int) :: Bool
  returns whether or not x is less than y
• (x::Int) <= (y::Int) :: Bool
  returns whether or not x is less than or equal to y
• (x::Int) > (y::Int) :: Bool
  returns whether or not x is greater than y
• (x::Int) >= (y::Int) :: Bool
  returns whether or not x is greater than or equal to y
• (x::Bool) && (y::Bool) :: Bool
  returns whether or not both x and y are True
• (x::Bool) && (y::Bool) :: Bool
  returns whether or not x and/or y are True

Conditions

• condition (x::Bool) (y::a) (z::a) :: a
  executes y if x is True. Otherwise execute z.

Combinators

• pass :: ()
  does nothing. Can be used as placeholder or for empty else condition.
• (x::a) $$ (y::b) :: ()
  first execute a and then b
• while (x::Bool) (y::a) :: ()
  executes y while x is True
• loop (x::a) :: () keeps executing x. Equivalent to a while (bool True) loop

Enviroment

• input :: Int
  consumes a value from the input list and returns it. If there are no values left, the program will terminate.
• output (x::Int) :: ()
  places an integer in the output list.
• save (x::Int) (y::Int) :: ()
  saves the value y with as key x.
• load (x::Int) :: Int
  loads the value with as key x.