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| 1 | +// |
| 2 | +// AstPrinter.swift |
| 3 | +// slox |
| 4 | +// |
| 5 | +// Created by Alejandro Martinez on 17/02/2017. |
| 6 | +// Copyright © 2017 Alejandro Martinez. All rights reserved. |
| 7 | +// |
| 8 | + |
| 9 | +import Foundation |
| 10 | + |
| 11 | +// Creates an unambiguous, if ugly, string representation of AST nodes. |
| 12 | +class AstPrinter: ExprVisitor, StmtVisitor { |
| 13 | + func print(expr: Expr) -> String { |
| 14 | + return expr.accept(visitor: self) |
| 15 | + } |
| 16 | + |
| 17 | + func print(stmt: Stmt) -> String { |
| 18 | + return stmt.accept(visitor: self) |
| 19 | + } |
| 20 | + |
| 21 | + // MARK: ExprVisitor |
| 22 | + |
| 23 | + func visitAssignExpr(_ expr: Expr.Assign) -> String { |
| 24 | + return parenthesize(name: "=", parts: expr.name.lexeme, expr.value) |
| 25 | + } |
| 26 | + |
| 27 | + func visitBinaryExpr(_ expr: Expr.Binary) -> String { |
| 28 | + return parenthesize(name: expr.op.lexeme, exprs: expr.left, expr.right) |
| 29 | + } |
| 30 | + |
| 31 | + func visitCallExpr(_ expr: Expr.Call) -> String { |
| 32 | + return parenthesize(name: "call", parts: expr.callee, expr.arguments) |
| 33 | + } |
| 34 | + |
| 35 | + func visitGetExpr(_ expr: Expr.Get) -> String { |
| 36 | + return parenthesize(name: ".", parts: expr.object, expr.name.lexeme) |
| 37 | + } |
| 38 | + |
| 39 | + func visitGroupingExpr(_ expr: Expr.Grouping) -> String { |
| 40 | + return parenthesize(name: "group", exprs: expr.expression) |
| 41 | + } |
| 42 | + |
| 43 | + func visitLiteralExpr(_ expr: Expr.Literal) -> String { |
| 44 | + guard let value = expr.value else { |
| 45 | + return "nil" |
| 46 | + } |
| 47 | + return String(describing: value) |
| 48 | + } |
| 49 | + |
| 50 | + func visitLogicalExpr(_ expr: Expr.Logical) -> String { |
| 51 | + return parenthesize(name: expr.op.lexeme, exprs: expr.left, expr.right) |
| 52 | + } |
| 53 | + |
| 54 | + func visitSetExpr(_ expr: Expr.Set) -> String { |
| 55 | + return parenthesize(name: "=", parts: expr.object, expr.name.lexeme, expr.value) |
| 56 | + } |
| 57 | + |
| 58 | + func visitSuperExpr(_ expr: Expr.Super) -> String { |
| 59 | + return parenthesize(name: "super", parts: expr.method) |
| 60 | + } |
| 61 | + |
| 62 | + func visitThisExpr(_ expr: Expr.This) -> String { |
| 63 | + return "this" |
| 64 | + } |
| 65 | + |
| 66 | + func visitUnaryExpr(_ expr: Expr.Unary) -> String { |
| 67 | + return parenthesize(name: expr.op.lexeme, exprs: expr.right) |
| 68 | + } |
| 69 | + |
| 70 | + func visitVariableExpr(_ expr: Expr.Variable) -> String { |
| 71 | + return expr.name.lexeme |
| 72 | + } |
| 73 | + |
| 74 | + func visitWhileStmt(_ stmt: Stmt.While) -> String { |
| 75 | + return parenthesize(name: "while", parts: stmt.condition, stmt.body) |
| 76 | + } |
| 77 | + |
| 78 | + private func parenthesize(name: String, exprs: Expr...) -> String { |
| 79 | + var output = "" |
| 80 | + |
| 81 | + output.append("(\(name)") |
| 82 | + |
| 83 | + for expr in exprs { |
| 84 | + output.append(" ") |
| 85 | + output.append(expr.accept(visitor: self)) |
| 86 | + } |
| 87 | + |
| 88 | + output.append(")") |
| 89 | + |
| 90 | + return output |
| 91 | + } |
| 92 | + |
| 93 | + // MARK: StmtVisitor |
| 94 | + |
| 95 | + func visitBlockStmt(_ stmt: Stmt.Block) -> String { |
| 96 | + var output = "" |
| 97 | + |
| 98 | + output.append("(block ") |
| 99 | + |
| 100 | + for statement in stmt.statements { |
| 101 | + output.append(statement.accept(visitor: self)) |
| 102 | + } |
| 103 | + |
| 104 | + return output |
| 105 | + } |
| 106 | + |
| 107 | + func visitClassStmt(_ stmt: Stmt.Class) -> String { |
| 108 | + var output = "" |
| 109 | + output += ("(class " + stmt.name.lexeme) |
| 110 | + |
| 111 | + // if (stmt.superclass != null) { |
| 112 | + // builder.append(" < " + print(stmt.superclass)); |
| 113 | + // } |
| 114 | + |
| 115 | + for method in stmt.methods { |
| 116 | + output += " " + method.accept(visitor: self) |
| 117 | + } |
| 118 | + |
| 119 | + output += ")" |
| 120 | + return output |
| 121 | + } |
| 122 | + |
| 123 | + func visitBreakStmt(_ stmt: Stmt.Break) -> String { |
| 124 | + return "(break)" |
| 125 | + } |
| 126 | + |
| 127 | + func visitExpressionStmt(_ stmt: Stmt.Expression) -> String { |
| 128 | + return parenthesize(name: ";", exprs: stmt.expression) |
| 129 | + } |
| 130 | + |
| 131 | + func visitFunctionStmt(_ stmt: Stmt.Function) -> String { |
| 132 | + var res = "(fun \(stmt.name.lexeme)" |
| 133 | + |
| 134 | + res += "(" |
| 135 | + for param in stmt.parameters { |
| 136 | + res += " \(param.lexeme)" |
| 137 | + } |
| 138 | + res += ") " |
| 139 | + |
| 140 | + if let stmtbody = stmt.body { |
| 141 | + for body in stmtbody { |
| 142 | + res += body.accept(visitor: self) |
| 143 | + } |
| 144 | + } else { |
| 145 | + // ... |
| 146 | + } |
| 147 | + |
| 148 | + return res |
| 149 | + } |
| 150 | + |
| 151 | + func visitIfStmt(_ stmt: Stmt.If) -> String { |
| 152 | + guard let elseBranch = stmt.elseBranch else { |
| 153 | + return parenthesize(name: "if", parts: stmt.condition, stmt.thenBranch) |
| 154 | + } |
| 155 | + |
| 156 | + return parenthesize(name: "if-else", parts: stmt.condition, stmt.thenBranch, elseBranch) |
| 157 | + } |
| 158 | + |
| 159 | + func visitPrintStmt(_ stmt: Stmt.Print) -> String { |
| 160 | + return parenthesize(name: "print", exprs: stmt.expression) |
| 161 | + } |
| 162 | + |
| 163 | + func visitReturnStmt(_ stmt: Stmt.Return) -> String { |
| 164 | + guard let value = stmt.value else { |
| 165 | + return "(return)" |
| 166 | + } |
| 167 | + return parenthesize(name: "return", parts: value) |
| 168 | + } |
| 169 | + |
| 170 | + func visitVarStmt(_ stmt: Stmt.Var) -> String { |
| 171 | + guard let initializer = stmt.initializer else { |
| 172 | + return parenthesize(name: "var", parts: stmt.name) |
| 173 | + } |
| 174 | + |
| 175 | + return parenthesize(name: "var", parts: stmt.name, "=", initializer) |
| 176 | + } |
| 177 | + |
| 178 | + private func parenthesize(name: String, parts: Any...) -> String { |
| 179 | + var output = "" |
| 180 | + |
| 181 | + output.append("(") |
| 182 | + |
| 183 | + output.append(name) |
| 184 | + |
| 185 | + for part in parts { |
| 186 | + output.append(" ") |
| 187 | + |
| 188 | + if let expr = part as? Expr { |
| 189 | + output.append(expr.accept(visitor: self)) |
| 190 | + } else if let stmt = part as? Stmt { |
| 191 | + output.append(stmt.accept(visitor: self)) |
| 192 | + } else if let token = part as? Token { |
| 193 | + output.append(token.lexeme) |
| 194 | + } else { |
| 195 | + output.append(String(describing: part)) |
| 196 | + } |
| 197 | + } |
| 198 | + |
| 199 | + output.append(")") |
| 200 | + |
| 201 | + return output |
| 202 | + } |
| 203 | +} |
| 204 | + |
| 205 | +// Chapter 5. Extra 3. In Reverse Polish Notation |
| 206 | +class AstRPNPrinter: ExprVisitor { |
| 207 | + func print(expr: Expr) -> String { |
| 208 | + return expr.accept(visitor: self) |
| 209 | + } |
| 210 | + |
| 211 | + func visitAssignExpr(_ expr: Expr.Assign) -> String { |
| 212 | + fatalError("unimplemented") |
| 213 | + } |
| 214 | + |
| 215 | + func visitBinaryExpr(_ expr: Expr.Binary) -> String { |
| 216 | + return "\(print(expr: expr.left)) \(print(expr: expr.right)) \(expr.op.lexeme)" |
| 217 | + } |
| 218 | + |
| 219 | + func visitCallExpr(_ expr: Expr.Call) -> String { |
| 220 | + fatalError("unimplemented") |
| 221 | + } |
| 222 | + |
| 223 | + func visitGetExpr(_ expr: Expr.Get) -> String { |
| 224 | + fatalError("unimplemented") |
| 225 | + } |
| 226 | + |
| 227 | + func visitGroupingExpr(_ expr: Expr.Grouping) -> String { |
| 228 | + return print(expr: expr.expression) |
| 229 | + } |
| 230 | + |
| 231 | + func visitLiteralExpr(_ expr: Expr.Literal) -> String { |
| 232 | + return String(describing: expr.value) |
| 233 | + } |
| 234 | + |
| 235 | + func visitLogicalExpr(_ expr: Expr.Logical) -> String { |
| 236 | + return "\(print(expr: expr.left)) \(print(expr: expr.right)) \(expr.op.lexeme)" |
| 237 | + } |
| 238 | + |
| 239 | + func visitSetExpr(_ expr: Expr.Set) -> String { |
| 240 | + fatalError("unimplemented") |
| 241 | + } |
| 242 | + |
| 243 | + func visitSuperExpr(_ expr: Expr.Super) -> String { |
| 244 | + fatalError("unimplemented") |
| 245 | + } |
| 246 | + |
| 247 | + func visitThisExpr(_ expr: Expr.This) -> String { |
| 248 | + fatalError("unimplemented") |
| 249 | + } |
| 250 | + |
| 251 | + func visitUnaryExpr(_ expr: Expr.Unary) -> String { |
| 252 | + return "\(print(expr: expr.right)) \(expr.op.lexeme)" |
| 253 | + } |
| 254 | + |
| 255 | + func visitVariableExpr(_ expr: Expr.Variable) -> String { |
| 256 | + fatalError("unimplemented") |
| 257 | + } |
| 258 | +} |
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