Description

I have provided a compiler for parenlet with Booleans on github.

Your task is to modify my lexer, parser, and compiler to add a print expression to parenlet, a small language described below:

‹expr›: 
           BOOL
           NUMBER
           ID
           ( let ( ID <expr> ) <expr> )
           ( add1 ‹expr› )
           ( print ‹expr› )

Your parser should produce an EPrim1 expression for the print:

type expr =
  | EBool of bool
  | ENum of int64
  | EId of string
  | ELet of string * expr * expr
  | EPrim1 of prim1 * expr

Semantics

The print expression takes 1 expression as argument. It should print the value of the argument. The print is an expression, so it should return a value, as determined by the argument.

Hints

Look at how we call error from assembly. There is already a print function in main.c that you could also call. What is the sequence of assembly instructions needed to call print with the correct arguments?

Example code

Here are some programs that should run in your finished compiler.

(print 3)

(print false)

(print (add1 3))

(let (x (print 4))
  (add1 x)) 

Deliverables

You should turn in your modified lexer.mll, parser.mly, compiler.ml and syntax.ml. You shouldn't need to make changes to other files (really).

If you want, run dune clean and zip up your entire parenlet directory.