Core Parser

Core Parser is a monadic parser for the Core Language written in Haskell.

This project has been developed for the Functional Languages course at the University of Padova, academic year 2019/2020. The Core language is defined in the book Implementing Functional Languages: a tutorial of Jones and Lester.

Data Type

The data type of Core-language expression, expr, is defined as follows:

data Expr a
  = EVar Name                   -- Variables
  | ENum Int                    -- Numbers
  | EConstr Int Int             -- Constructor tag arity
  | EAp (Expr a) (Expr a)       -- Applications
  | ELet                        -- Let(rec) expressions
      IsRec                       -- boolean with True = recursive
      [Def a]                     -- Definitions
      (Expr a)                    -- Body of let(rec)
  | ECase                       -- Case expression
      (Expr a)                    -- Expression to scrutinise
      [Alter a]                   -- Alternatives
  | ELam [a] (Expr a)           -- Lambda abstractions
  deriving (Show, Eq)

BNF Grammar

The Core Language is defined by the following Backus-Naur Form:

Operators Associativity

The language's operators use the associativity rules defined in the following table:

Precedence	Associativity	Operator
6	Left	Application
5	Right	*
	None	/
4	Right	+
	None	-
3	None	==, ~=, >, >=, <, <=
2	Right	&
1	Right	`

Commands

• stack build: compiles the parser
• stack exec core-parser-exe: executes the parser
• stack test: runs unit tests (there are 20 unit tests, all passing)

Example

By default, the main entrypoint reads a Core source file from the ./example.core file. You can create new examples and choose to import them in the program.