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| 1 | +case class Token(tokenType: TokenType, lexeme: String, line: Int) |
| 2 | + |
| 3 | +enum TokenType: |
| 4 | + // Single-character tokens. |
| 5 | + case MINUS, PLUS, SLASH, STAR, |
| 6 | + |
| 7 | + // One or two character tokens. |
| 8 | + BANG, BANG_EQUAL, |
| 9 | + EQUAL, EQUAL_EQUAL, |
| 10 | + GREATER, GREATER_EQUAL, |
| 11 | + LESS, LESS_EQUAL |
| 12 | + |
| 13 | +enum Expr { |
| 14 | + case Binary(left: Expr, operator: Token, right: Expr) |
| 15 | +} |
| 16 | + |
| 17 | +object Interpreter: |
| 18 | + import Expr._ |
| 19 | + import TokenType._ |
| 20 | + |
| 21 | + def eval(expr: Expr): String | Int | Double | Boolean | Unit = |
| 22 | + expr match |
| 23 | + case Binary(left, op, right) => |
| 24 | + val l = eval(left) |
| 25 | + val r = eval(right) |
| 26 | + (l, r, op.tokenType) match |
| 27 | + case (l: Double, r: Double, PLUS) => l + r |
| 28 | + case (l: Int, r: Int, PLUS) => l + r |
| 29 | + case (l: Double, r: Int, PLUS) => l + r |
| 30 | + case (l: Int, r: Double, PLUS) => l + r |
| 31 | + case (l: String, r: String, PLUS) => l + r |
| 32 | + case (l: Double, r: Double, MINUS) => l - r |
| 33 | + case (l: Int, r: Int, MINUS) => l - r |
| 34 | + case (l: Double, r: Int, MINUS) => l - r |
| 35 | + case (l: Int, r: Double, MINUS) => l - r |
| 36 | + case (l: Double, r: Double, STAR) => l * r |
| 37 | + case (l: Int, r: Int, STAR) => l * r |
| 38 | + case (l: Double, r: Int, STAR) => l * r |
| 39 | + case (l: Int, r: Double, STAR) => l * r |
| 40 | + case (l: Double, r: Double, SLASH) => l / r |
| 41 | + case (l: Int, r: Int, SLASH) => l / r |
| 42 | + case (l: Double, r: Int, SLASH) => l / r |
| 43 | + case (l: Int, r: Double, SLASH) => l / r |
| 44 | + case (l: Double, r: Double, GREATER) => l > r |
| 45 | + case (l: Int, r: Int, GREATER) => l > r |
| 46 | + case (l: Double, r: Int, GREATER) => l > r |
| 47 | + case (l: Int, r: Double, GREATER) => l > r |
| 48 | + case (l: String, r: String, GREATER) => l > r |
| 49 | + case (l: Double, r: Double, LESS) => l < r |
| 50 | + case (l: Int, r: Int, LESS) => l < r |
| 51 | + case (l: Double, r: Int, LESS) => l < r |
| 52 | + case (l: Int, r: Double, LESS) => l < r |
| 53 | + case (l: String, r: String, LESS) => l < r |
| 54 | + case (l: Double, r: Double, LESS_EQUAL) => l <= r |
| 55 | + case (l: Int, r: Int, LESS_EQUAL) => l <= r |
| 56 | + case (l: Double, r: Int, LESS_EQUAL) => l <= r |
| 57 | + case (l: Int, r: Double, LESS_EQUAL) => l <= r |
| 58 | + case (l: String, r: String, LESS_EQUAL) => l <= r |
| 59 | + case (l: Double, r: Double, GREATER_EQUAL) => l >= r |
| 60 | + case (l: Int, r: Int, GREATER_EQUAL) => l >= r |
| 61 | + case (l: Double, r: Int, GREATER_EQUAL) => l >= r |
| 62 | + case (l: Int, r: Double, GREATER_EQUAL) => l >= r |
| 63 | + case (l: String, r: String, GREATER_EQUAL) => l >= r |
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