// Shunting Yard Algorithm

// by Edsger Dijkstra

// ========================

object C3a {

// type of tokens

type Toks = List[String]

// the operations in the basic version of the algorithm

val ops = List("+", "-", "*", "/")

// the precedences of the operators

val precs = Map("+" -> 1,

		"-" -> 1,

		"*" -> 2,

		"/" -> 2)

// helper function for splitting strings into tokens

def split(s: String) : Toks = s.split(" ").toList

// ADD YOUR CODE BELOW

//======================

// (1) 

def is_op(op: String) : Boolean = ???

def prec(op1: String, op2: String) : Boolean = ???

def syard(toks: Toks, st: Toks = Nil, out: Toks = Nil) : Toks = ???

// test cases

//syard(split("3 + 4 * ( 2 - 1 )"))  // 3 4 2 1 - * +

//syard(split("10 + 12 * 33"))       // 10 12 33 * +

//syard(split("( 5 + 7 ) * 2"))      // 5 7 + 2 *

//syard(split("5 + 7 / 2"))          // 5 7 2 / +

//syard(split("5 * 7 / 2"))          // 5 7 * 2 /

//syard(split("9 + 24 / ( 7 - 3 )")) // 9 24 7 3 - / +

//syard(split("3 + 4 + 5"))           // 3 4 + 5 +

//syard(split("( ( 3 + 4 ) + 5 )"))    // 3 4 + 5 +

//syard(split("( 3 + ( 4 + 5 ) )"))    // 3 4 5 + +

//syard(split("( ( ( 3 ) ) + ( ( 4 + ( 5 ) ) ) )")) // 3 4 5 + +

// (2) 

def compute(toks: Toks, st: List[Int] = Nil) : Int = ???

// test cases

// compute(syard(split("3 + 4 * ( 2 - 1 )")))  // 7

// compute(syard(split("10 + 12 * 33")))       // 406

// compute(syard(split("( 5 + 7 ) * 2")))      // 24

// compute(syard(split("5 + 7 / 2")))          // 8

// compute(syard(split("5 * 7 / 2")))          // 17

// compute(syard(split("9 + 24 / ( 7 - 3 )"))) // 15

}