You can build using Stack or by make all. Caution: the latter will download stack and use it to set up the program and then copy binary to local directory.

Basic instruction of running the language interpreter:

• ./interpreter <filename> will run from the file
• ./interpreter will run from stdin

Code examples are placed in good (positive) and bad (negative) directories. You can just run them with interpreter. Positive examples (they're a test suite too) should all result in True.

Language features:

• strongly typed lambda calculus
• type inference using H-M algorithm W (with polymorphism)
• type annotations
• explicite laziness
• if-then-else and operators being only syntactic sugar for calling builtin functions
• "undefined" explicite-fail primitive
• Syntax for defining your own operators
• some light syntactic sugar (ie. multivariable lambdas)
• error handling parse-, typecheck- and run-time with file/line number/column references

Non-implemented features:

• classes, monads and IO

Standard library implemented in stdlib.ffl.

Match expression syntax is non-obvius. There is:

match expression with
  Constructor1 param1 param2 -> result1 | Constructor2 -> result2 end

where end is optional and used to force finish match expression, very useful in case of nested matches which would be unimplementable otherwise.