let rec evalLogicExpr expr =
    match expr with
    | Prim ("=", oper1, oper2)   ->  (evalLogicExpr oper1) =  (evalLogicExpr oper2)
    | Prim ("<>", oper1, oper2)  ->  (evalLogicExpr oper1) <> (evalLogicExpr oper2)
    | Prim (">", oper1, oper2)   ->  (evalLogicExpr oper1) >  (evalLogicExpr oper2)
    | Prim ("<", oper1, oper2)   ->  (evalLogicExpr oper1) <  (evalLogicExpr oper2)
    | Prim (">=", oper1, oper2)  ->  (evalLogicExpr oper1) >= (evalLogicExpr oper2)
    | Prim ("<=", oper1, oper2)  ->  (evalLogicExpr oper1) <= (evalLogicExpr oper2)
    | _                          ->  failwithf "Syntax error"

let rec evalNumExpr expr =
    match expr with
    | Prim ("-", oper1, oper2)   ->  (evalNumExpr oper1) -  (evalNumExpr oper2)
    | Prim ("+", oper1, oper2)   ->  (evalNumExpr oper1) +  (evalNumExpr oper2)
    | Prim ("*", oper1, oper2)   ->  (evalNumExpr oper1) *  (evalNumExpr oper2)
    | Prim ("/", oper1, oper2)   ->  (evalNumExpr oper1) /  (evalNumExpr oper2)
    | Prim ("%", oper1, oper2)   ->  (evalNumExpr oper1) %  (evalNumExpr oper2)
    | _                          -> failwithf "Error in syntax"

let evalPrim expr =
    match expr with
    | Prim ("-", _, _)   ->  evalNumExpr expr
    | Prim ("+", _, _)   ->  evalNumExpr expr
    | Prim ("*", _, _)   ->  evalNumExpr expr
    | Prim ("/", _, _)   ->  evalNumExpr expr
    | Prim ("%", _, _)   ->  evalNumExpr expr
    | Prim ("=", _, _)   ->  evalLogicExpr expr
    | Prim ("<>", _, _)  ->  evalLogicExpr expr
    | Prim (">", _, _)   ->  evalLogicExpr expr
    | Prim ("<", _, _)   ->  evalLogicExpr expr
    | Prim (">=", _, _)  ->  evalLogicExpr expr
    | Prim ("<=", _, _)  ->  evalLogicExpr expr
    | _     ->  failwithf "%A" "Incorrect syntax"

let rec eval (expr : expr) =
    match expr with
    | Prim (_, _, _)    -> evalPrim expr
    | _                 -> failwithf "Syntax error"