Pretty printer for dpc


I have provided a pretty printer for depython on github, but it's imcomplete, it can't pretty print if or let expressions.

Your task is to modify our pretty printer to pretty print any valid expr.

           add1 ( ‹expr› )
           sub1 ( ‹expr› )
           ( <expr> )
           <expr> + <expr>
           <expr> - <expr>
           <expr> * <expr>
           if <expr>: <expr> else: <expr>
           let IDENTIFIER = <expr> in <expr>

Your pretty printer should produce a printed representation of abstract syntax as shown in as a string.

type expr =
  | Num of int64
  | Add1 of expr
  | Sub1 of expr
  | EPrim2 of prim2 * expr * expr
  | Id of string
  | Let of string * expr * expr
  | If of expr * expr * expr

Example code

There's sample code in github. To run it you will need menhir and dune installed. I used opam to install mine.

You can parse a sample depython program using:

$ dune build
$ dune exec ./prettier.exe 4410.dp
Num 4410

After modifying the lexer and parser you should be able to parse a program like the examples in lecture 4.

$ cat ifif.dp
if 0:
      if 1:

The current pretty printer can't understand this program:

$ dune exec ./prettier.exe ifif.dp

After you complete the assignment, the output should be:

If (Num 0L, Num 7L, If (Num 1L, Num 9L, Num 42L))


You should turn in your modified in moodle. You shouldn't need to make changes to other files.