%{
  open Arith
%}

%token <int> INT
%token <string> VAR
%token PLUSEQ MINUSEQ DIVEQ MULEQ MODEQ EQ
%token PLUS MINUS MUL DIV
%token LT GT EQEQ
%token QUESTION COLON
%token LPAREN RPAREN
%token EOF

%right PLUSEQ MINUSEQ DIVEQ MULEQ MODEQ EQ
%right QUESTION COLON
%left PLUS MINUS
%left MUL DIV
%left GT LT
%right UMINUS UPLUS

%start <Arith.expr> main

%%

main:
  | expr EOF { $1 }

expr:
  | v=VAR PLUSEQ e=expr { Assign (Add, v, e) } 
  | v=VAR MINUSEQ e=expr { Assign (Sub, v, e) } 
  | v=VAR MULEQ e=expr { Assign (Mul, v, e) } 
  | v=VAR DIVEQ e=expr { Assign (Div, v, e) }
  | expr PLUS expr  { Binop (Add, $1, $3) }
  | expr MINUS expr { Binop (Sub, $1, $3) }
  | expr MUL expr  { Binop (Mul, $1, $3) }
  | expr DIV expr { Binop (Div, $1, $3) }
  | expr LT expr { Binop (Lt, $1, $3) }
  | expr GT expr { Binop (Gt, $1, $3) }
  | expr EQEQ expr { Binop (Eq, $1, $3) }
  | expr QUESTION expr COLON expr { Ternary ($1, $3, $5) }


  | PLUS expr  %prec UPLUS  { $2 }
  | MINUS expr %prec UMINUS { Neg $2 }

  | INT        { Int $1 }
  | VAR        { Var $1 }
  | LPAREN expr RPAREN { $2 }