Fouine: An OCaml repository from poechsel

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Compile:

Make sure ocamlbuild is installed. Then just type make

How to use:

By default ./fouine is an interpretor. To use it type ./fouine. Several options are available:

-debug to pretty print the instructions after they are inputted, or complementary informations when compiling.
-nocoloration to deactivate the syntax coloration. It is activated by default.
-noinference to deactivate type inference (activated by default)
-interm FILE to save the compiled code in the file FILE
-o FILE to save transformed code in a file
-R to activate the transformation suppressing references
-E to activate the cps transformation (expressions are made by continuations)
ER to activate both transformations
-nobuildins to deactivate the buildins
-noinference to deactivate the inference
-machine (Z|S|J) if you want to compile your fouine file. Z|S|J determines for which machine it will be compiled. It is important to note that the different machines don't support pattern matching and constructors !
- Z is a ZINC machine
- S is a secd machine
- J is a joint interpretation / secd machine. It will interpret the program until "pure" expressions (only made of arithmetical expressions) is found. It then switch to a secd machine for this expression.
a file can be passed to ./fouine. In that case, this file will be executed. Otherwise ./fouine will be launched under the repl mode

The script test.sh will test Fouine with the files found in the folder tests/

Syntax:

The syntax - and the functionnalities - are similar with Caml. Here is a summary:

Basic mathematical operators : +,-, /, *, =, <>, <, >, <=, >=, and, or, not.
- Operators +,-, /, * have types int -> int-> int.
- and, or, not have types bool-> bool-> bool and bool->bool
- =, <>, <, >, <=, >= have types 'a->'a->int Depending on how the interpreter / compiler is launch, these operators are either buildins or not. With the option -nobuildins, or if it is compiled for a ZINC machine, then they aren't buildins. Otherwise they are : we can therefore change their behaviour by redefining +, *, ...
Branching: if condition then foo else bar. foo and bar must have the same type. Expressions like if cond then expr works only if expr is of type unit
Functions: fun a-> fun b -> expr is a two variables anonymous fonction
Affectation and variables:
- let ident = exp in expression will affect to the identifier ident the value expr. let ident a b c = expr in expression is a shortcut for let ident = fun a-> fun b-> fun c->expr in expression. Expressions of the form let ident = expr are only accepted on the top level.
- let rec ident = expr will behave almost identically as let ident = expr: expr is assigned to ident, but ident can be present in expr, thus allowing recursive functions.
References. References are almost likes pointer. They are mutable. We can access to the value of a reference with the operator !, and modify the value of a reference with := (type ref 'a -> 'a -> unit).
```
let a = ref 6 in
let _ = a := 8 in
!a (* <- it is 8 *)
```
Underscore (_). It matches everything. These instructions are valid:
- let _ = expr
- let f x _ = x in f
Exceptions:
- An exception can be emitted with the instruction raise n where n is an integer.
- An exception can be caught with a bloc of the form try foo with E x -> bar. If x is a constant, then bar is executed only if foo raised an exception having x has value. Otherwise, bar is executed if foo raised an exception
array: integer fixed-length arrays can be created with the syntax makeArray n where n is the length. An element can be accessed with the syntax array.(index), and affected with array.(index) <- value
prInt: prInt expr will print expr and return the value expr. It has type int -> int
Files. The command open "file" will open a fouine file and will load its code as a module (functions declared in this file will be accessible with the syntax file.function. If the file doesn't exists, or if it contains a parsing error, the loaded code will be (). Beware: paths are relatives to the interpreter files
Tuples: (a, b, c) will create a three dimensionnal tuple. You can match on the elements: let x, y = 1, 2
Types and constructors
- Declarations are like in Caml with the syntax: type ('a, ..., 'b) type_name = | Constr1 of (type_arguments1) .... | Constrn of (type_argumentsn)
- Types are recursives: let 'a test = None of 'a test
- Constructors aren't force to have arguments
Pattern matching: expression like let 0, (), (x, _), Constr y = .... or fun (x, Constr (a, b)) -> ... are valid. You can explicitely match a value with the syntax match expr with | pattern_1 -> expr1 | ... -> ... | pattern_n -> exprn. If expr matches with patterni, then expri will be executed
;; are required at the end of an expression
We can redefined a number of operators (infix or prefix). The syntax is the same than in caml: let (@@) a b = ....
List: An empty list can be build with [], two list can be concatenated with @ and an element can be inserted to the front with ::. They are compatible with pattern matching (their definition is simply type 'a list = None | Elem of ('a * 'a list)). They are not working with compilation.
modules. A module can be defined as follow: module Test : sig ... end = struct .. end;;. Signatures can be also provided module type TestSig = sig type t;; type t2 = int;; val f : int -> int -> int end;; module Test : TestSig = struct type t = int;; let f a b = a + b;; end;; It is important to note that signatures only checks for the presence of the elements. They are not as powerfull as in OCaml.
Type constraints. Type constraints are working if no ref are presents. let f x : int = x;; int -> int let f (x : bool) = x;; bool -> bool ((fun x -> x) : int -> int)
Base types: 'a -> 'b, 'a ref, int array, int, bool

The constructors of our types have only an argument which is a tuple. From there, certains expressions which are not working in Caml are working in Fouine:

>>> type 'a ok = Machin of 'a;;
>>> let a = Machin 3;;
val a : int ok = Machin (3)
>>> let Machin b = a;;
val b : int = 3

Code transformations

Two types transformations can be applied. The first one will remove the references and simulate them using an array (transformation R) The second one do a cps transformation of the code (transformation E). Recursive functions are transformed using an Y-combinator. The two transformations can be applied at the same time (transformation ER). Typing errors can then appear because our fouine langage is converted into a subset of fouine very similar to lambda calculus. Therefore our typing system isn't powerfull enough to type these expressions. (but the same problem arise in Caml)

Architecture:

inference.ml: type inference
buildins.ml: buildins functions definition (apport from basic mathematical operators)
inference_old.ml: old type inference. Kept for archeleogical purposes
transformations.ml: code transformations
prettyprint.ml: fouine pretty printer
binop.ml: binary operators functions
shared.ml: buildins declarations and variables environments
types.ml: type definitions and utilities around types
commons.ml: file containing elements usefull everywhere in the code
errors.ml: errors les erreurs
file.ml: everything to deal with files
main.ml: repl, main and loading files
interpret.ml: interpreter
compilB.ml: fouine to SECD machine bytecode compilation
secdB.ml: to execute SECD bytecode
utils.ml: display, debug and utilities functions for the SECD simulator
bruijn.ml: De bruijn indices
dream.ml: environment used for the secd and the bruijn indices
expr.ml: declaration of the types used to define our ast
parser.mly, lexer.mll: parsing and lexing
bruijnZ.ml, compilZ.ml, secdZ.ml: de bruijn indices, compilation and simulation for a ZINC machine
jit.ml: mixed machine

poechsel/Fouine

Compile:

How to use:

Syntax:

Code transformations

Architecture: