feat: Support basic expression

lib/ast.ml

@@ -0,0 +1,34 @@
+(* lib/ast.ml *)
+
+type binary_operator = Add | Substract | Multiply | Divide
+
+type expression =
+  | IntegerLiteral of int
+  | BinaryExpression of binary_operator * expression * expression
+
+type statement = ExpressionStatement of expression
+type source_file = SourceFile of statement list
+
+(* Print AST *)
+
+let string_of_binary_operator = function
+  | Add -> "Add"
+  | Substract -> "Substract"
+  | Multiply -> "Multiply"
+  | Divide -> "Divide"
+
+let rec string_of_expression = function
+  | IntegerLiteral i -> "IntegerLiteral(" ^ string_of_int i ^ ")"
+  | BinaryExpression (op, e1, e2) ->
+      "BinaryExpression("
+      ^ string_of_binary_operator op
+      ^ ", " ^ string_of_expression e1 ^ ", " ^ string_of_expression e2 ^ ")"
+
+let string_of_statement = function
+  | ExpressionStatement e ->
+      "ExpressionStatement(" ^ string_of_expression e ^ ")"
+
+let string_of_source_file = function
+  | SourceFile stmts ->
+      let stmt_strings = List.map string_of_statement stmts in
+      "SourceFile([" ^ String.concat ", " stmt_strings ^ "])"

lib/dune

@@ -1,2 +1,21 @@
+;lib/dune
+
 (library
- (name croissant))
+ (name lexer)
+ (modules lexer)
+ (libraries parser))
+
+(library
+ (name parser)
+ (modules parser)
+ (libraries ast))
+
+(library
+ (name ast)
+ (modules ast))
+
+(menhir
+ (modules parser))
+
+(ocamllex
+ (modules lexer))

lib/lexer.mll

@@ -0,0 +1,28 @@
+(* lib/lexer.mll *)
+{
+  open Parser
+  exception Error of char
+}
+
+let line_comment = "//" [^ '\n']*
+
+let digit = ['0'-'9']
+let integer = digit+
+
+rule token = parse
+   |  [' ' '\t'] | line_comment { token lexbuf }
+   | ['\n'] { Lexing.new_line lexbuf; token lexbuf }
+
+   | '+' { PLUS }
+   | '-' { MINUS }
+   | '*' { TIMES }
+   | '/' { DIVIDE }
+   | ';' { SEMICOLON }
+
+   | integer as lxm { INT(int_of_string lxm) }
+
+   | '(' { LPAREN }
+   | ')' { RPAREN }
+
+   | eof { EOF }
+   | _ as c { raise (Error c) }

lib/parser.mly

@@ -0,0 +1,51 @@
+/* lib/parser.mly */
+%{
+   open Ast
+%}
+
+%token <int> INT
+
+%token PLUS "+"
+%token MINUS "-"
+%token TIMES "*"
+%token DIVIDE "/"
+
+%token LPAREN "("
+%token RPAREN ")"
+
+%token SEMICOLON ";"
+
+%token EOF
+
+%left "+" "-"
+%left "*" "/"
+//%nonassoc UMINUS
+
+%start main
+%type <source_file> main
+
+%%
+
+main:
+  | statements EOF { SourceFile($1) }
+
+statements:
+  | statement ";" { [$1] }
+  | statement ";" statements { $1 :: $3 }
+
+statement:
+  | expression { ExpressionStatement($1) }
+
+expression:
+  | literal { $1 }
+  | binary_expression { $1 }
+  | "(" expression ")" { $2 }
+
+literal:
+  | INT { IntegerLiteral($1) }
+
+binary_expression:
+  | e1=expression PLUS e2=expression { BinaryExpression(Add, e1, e2) }
+  | e1=expression MINUS e2=expression { BinaryExpression(Substract, e1, e2) }
+  | e1=expression TIMES e2=expression { BinaryExpression(Multiply, e1, e2) }
+  | e1=expression DIVIDE e2=expression { BinaryExpression(Divide, e1, e2) }