Pascal-Syntax.ml: ISO Pascal's syntax formalized in OCaml type system

README.md

I have been a lot into formalism lately, and I am trying to sort out my thoughts. Let's just say I am not the sharpest crayon in lil jimmy's lunchbox (which his over-worked mom filled with crayons!).

Pascal-Syntax.ml is an OCaml interface file (which is akin to C's .h files) that defines the syntax of ISO Pascal. You can download the standard from here:

https://www.cs.utexas.edu/users/novak/iso7185.pdf

ISO Pascal differs from widely-used dialects of Pascal (all of which FPC supports!) in a way that it does not support objects, but that is not the only thing it does not support!

Pascal's author, Niklaus Wirth died just a few years ago. It's really sad to see Pascal forgotten. I aim to create a Pascal compiler, or interpreter, or even a translator to another algorithmic language (people often call these 'transpilers' but this is obviously folk colliqualism...).

I think what I can offer would be verification. Or maybe partial evalution, meta-tracing. I shall decide.

This will of course be used to create an AST, or in the parser/lexer.

I am a beginner in all this ('this' meaning life, but also everything else). Please let me know. I am not very apt at ML-like syntax.

chubakbidpaa [at] riseup [dot] net

I am .chubak ( [dot] chubak ) on Discord.

Thanks.

Pacal-Syntax.ml

(* Formalism for ISO-7185:1990 "Pascal" Syntax *)
(* These will be extended into an AST *)
(* ISO Pascal is different from Delphi *)
(* Please submit your comments to chubakbidpaa [at] riseup [dot] net *)

type pas_kw = And | Array | Begin | Case | Const
            | Div | Do | Downto | Else | End
            | File | For | Function | Goto 
            | If | In | Label | Mod | Nil
            | Not | Of | Or | Packed | Procedure
            | Program | Record | Repeat | Set 
            | Then | To | Until | Var | While | With

and pas_val = 
    Number of float | CharString of string | Id of string

and pas_type_val =
  | SimpleType of pas_simple_type
  | OrginalType of pas_ordinal_type
  | StructuredType of pas_structured_type * bool
  | PointerType of string
  | FuncType of pas_func_type
  | Alias of string

and pas_simple_type = IntegerType | RealType | BoolType | CharType

and pas_ordinal_type = 
  | Enumerated of string list | Range of (int * int) list

and pas_structured_type =
  | Array of pas_array_unit list
  | Record of { 
      fixed_part: pas_rec_fixed_part list option;
      variant_part: pas_rec_variant_part list option;
    }
  | Set of pas_type_val
  | File of pas_type_val

and pas_array_unit = 
  { index_type: pas_type_val; component_type: string; } 

and pas_rec_fixed_part = { names: string list; 
                           typs: pas_type_val list; }
and pas_rec_variant_part = { selector: (string * string option);
                             variants: (string list * pas_type_val) list; }

and pas_func_type = { name: string; 
                      params: pas_param list; 
                      result_type: pas_type_val; }

and pas_param = { name: string option; typ: pas_type_val; }

and pas_block = LabelDecl of pas_label list
              | ConstDecl of pas_const list
              | TypeDecl of pas_type list
              | VarDecl of pas_var list
              | ProcDecl of pas_proc list
              | FuncDecl of pas_func list
              | StmtDecl of pas_stmt list

and pas_label = { name: string; value: int }

and pas_const = { name: string; value: pas_val; typ: pas_type_val; }

and pas_var = | Basic of { name: string; points: bool; index: pas_val list; }
              | Long of pas_var list

and pas_type = { name: string; value: pas_type_val; }

and pas_proc = { name: string; params: pas_param list; body: pas_stmt list; }

and pas_func = { typ: pas_func_type; body: pas_stmt list; }

and pas_stmt = | BlockStmt of pas_block
               | Expression of pas_expr
               | Controlflow of pas_control
               | Assignment of pas_var * pas_expr

and pas_expr = | Var of pas_var
               | Call of pas_var * pas_val list
               | Infix of  { left: pas_expr list; 
                             right: pas_expr list; 
                             operator: pas_infixop; }
               | Prefix of pas_prefixop * pas_expr

and pas_infixop = Add | Sub | Mul | Div | IDiv | Mod | Eq | Ne | Lt | Le
                | Gt | Ge | BitAnd | BitOr | Xor | And | Or | Union
                | Diff | Inter | SymDiff | Incl | Cat

and pas_prefixop = UMin | UPos | BitNot | Deref | AddrOf

and pas_control = | If of { cond: pas_expr; 
                            branches: (pas_expr * pas_block) list;
                            clause: pas_block }
                  | Case of { disc: pas_expr; 
                              clauses: (pas_expr * pas_block);
                              default: pas_block; }
                  | Loop of { starter: pas_stmt; 
                              ender: pas_stmt;
                              ranger: pas_kw;
                              block: pas_block;
                            }
                  | While of  { cond: pas_expr;
                                block: pas_block; }
                  | RepeatUntil of { block: pas_block; cond: pas_expr; }
                  | With of { var: pas_var; block: pas_block; }
                  | Goto of string

and pas_program = { name: string; blocks: pas_block list; }