2d:null 2e:["$","title",null,{"children":"JSLox as of the end of Ch 9, \"Control Flow\" | Thomas Ballinger | Observable"}] 33:T8fb,TokenType = { class TokenType { constructor(name) { this.name = name; } toString() { return `TokenType.${this.name}`; } } // Single-character tokens. (TokenType.LEFT_PAREN = new TokenType('LEFT_PAREN')), (TokenType.RIGHT_PAREN = new TokenType('RIGHT_PAREN')), (TokenType.LEFT_BRACE = new TokenType('LEFT_BRACE')), (TokenType.RIGHT_BRACE = new TokenType('RIGHT_BRACE')), (TokenType.COMMA = new TokenType('COMMA')), (TokenType.DOT = new TokenType('DOT')), (TokenType.MINUS = new TokenType('MINUS')), (TokenType.PLUS = new TokenType('PLUS')), (TokenType.SEMICOLON = new TokenType('SEMICOLON')), (TokenType.SLASH = new TokenType('SLASH')), (TokenType.STAR = new TokenType('STAR')), // One or two character tokens. (TokenType.BANG = new TokenType('BANG')), (TokenType.BANG_EQUAL = new TokenType('BANG_EQUAL')), (TokenType.EQUAL = new TokenType('EQUAL')), (TokenType.EQUAL_EQUAL = new TokenType('EQUAL_EQUAL')), (TokenType.GREATER = new TokenType('GREATER')), (TokenType.GREATER_EQUAL = new TokenType('GREATER_EQUAL')), (TokenType.LESS = new TokenType('LESS')), (TokenType.LESS_EQUAL = new TokenType('LESS_EQUAL')), // Literals. (TokenType.IDENTIFIER = new TokenType('IDENTIFIER')), (TokenType.STRING = new TokenType('STRING')), (TokenType.NUMBER = new TokenType('NUMBER')), // Keywords. (TokenType.AND = new TokenType('AND')), (TokenType.CLASS = new TokenType('CLASS')), (TokenType.ELSE = new TokenType('ELSE')), (TokenType.FALSE = new TokenType('FALSE')), (TokenType.FUN = new TokenType('FUN')), (TokenType.FOR = new TokenType('FOR')), (TokenType.IF = new TokenType('IF')), (TokenType.NIL = new TokenType('NIL')), (TokenType.OR = new TokenType('OR')), (TokenType.PRINT = new TokenType('PRINT')), (TokenType.RETURN = new TokenType('RETURN')), (TokenType.SUPER = new TokenType('SUPER')), (TokenType.THIS = new TokenType('THIS')), (TokenType.TRUE = new TokenType('TRUE')), (TokenType.VAR = new TokenType('VAR')), (TokenType.WHILE = new TokenType('WHILE')), (TokenType.LET = new TokenType('LET')), (TokenType.IN = new TokenType('IN')), (TokenType.EOF = new TokenType('EOF')); return TokenType; }34:Tf9f,scanTokens = source => { // a bunch of stateful helpers here use this state let start = 0; let current = 0; let line = 1; let tokens = []; const isAtEnd = () => current >= source.length; const advance = () => { return source[current++]; }; const addToken = (type, literal = null) => { const text = source.substring(start, current); tokens.push(new Token(type, text, literal, line)); }; const match = expected => { if (isAtEnd()) return false; if (source[current] != expected) return false; current++; return true; }; const peek = () => { if (isAtEnd()) return '\0'; return source.charAt(current); }; const peekNext = () => { if (current + 1 >= source.length) return '\0'; return source.charAt(current + 1); }; const string = () => { while (peek() != '"' && !isAtEnd()) { if (peek() == '\n') line++; advance(); } // Unterminated string. if (isAtEnd()) { reportError(line, "Unterminated string."); return; } // The closing ". advance(); // Trim the surrounding quotes. const value = source.substring(start + 1, current - 1); addToken(TokenType.STRING, value); }; const isDigit = c => { return c >= '0' && c <= '9'; }; const number = () => { while (isDigit(peek())) { advance(); } // Look for a fractional part. if (peek() == '.' && isDigit(peekNext())) { // Consume the "." advance(); while (isDigit(peek())) advance(); } addToken(TokenType.NUMBER, parseFloat(source.substring(start, current))); }; const isAlpha = c => { return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_'; }; const isAlphaNumeric = c => { return isAlpha(c) || isDigit(c); }; const identifier = () => { while (isAlphaNumeric(peek())) advance(); const text = source.substring(start, current); let type = keywords[text]; if (type === undefined) { type = TokenType.IDENTIFIER; } addToken(type); }; const scanToken = () => { const c = advance(); switch (c) { case '(': addToken(TokenType.LEFT_PAREN); break; case ')': addToken(TokenType.RIGHT_PAREN); break; case '{': addToken(TokenType.LEFT_BRACE); break; case '}': addToken(TokenType.RIGHT_BRACE); break; case ',': addToken(TokenType.COMMA); break; case '.': addToken(TokenType.DOT); break; case '-': addToken(TokenType.MINUS); break; case '+': addToken(TokenType.PLUS); break; case ';': addToken(TokenType.SEMICOLON); break; case '*': addToken(TokenType.STAR); break; case '!': addToken(match('=') ? TokenType.BANG_EQUAL : TokenType.BANG); break; case '=': addToken(match('=') ? TokenType.EQUAL_EQUAL : TokenType.EQUAL); break; case '<': addToken(match('=') ? TokenType.LESS_EQUAL : TokenType.LESS); break; case '>': addToken(match('=') ? TokenType.GREATER_EQUAL : TokenType.GREATER); break; case '/': if (match('/')) { // A comment goes until the end of the line. while (peek() != '\n' && !isAtEnd()) advance(); } else { addToken(TokenType.SLASH); } break; case ' ': case '\r': case '\t': // Ignore whitespace. break; case '\n': line++; break; case '"': string(); break; default: if (isDigit(c)) { number(); } else if (isAlpha(c)) { identifier(); } else { reportError(line, "Unexpected character."); } break; } }; while (!isAtEnd()) { start = current; scanToken(); } tokens.push(new Token(TokenType.EOF, '', '', line)); return tokens; }35:T61c,defineAst = { const defineClass = (base_class_name, class_name, fields) => `class ${class_name} extends ${base_class_name} { constructor(${fields.join(', ')}) { super(); ${fields.map(field => ` this.${field} = ${field};`).join('\n')} } accept(visitor) { return visitor.visit_${class_name}${base_class_name}(this); } }`; const defineAst = (base_class_name, type_specs) => { const classStrings = []; const visitor_method_strings = []; const classNames = []; for (let type_spec of type_specs) { const class_name = type_spec.split(':')[0].trim(); classNames.push(class_name); const fields = type_spec .split(':')[1] .trim() .split(', '); classStrings.push(defineClass(base_class_name, class_name, fields)); visitor_method_strings.push( ` visit_${class_name}${base_class_name}() { throw Error(${'`visit method '}"visit_${class_name}${base_class_name}" not implemented on ${"${this.constructor.name}`"}); }` ); } return `${base_class_name} = { // GENERATED - DO NOT MANUALLY EDIT! // To update it, modify the defineAst below and manually copy/paste its output into the next cell. class Visitor { ${visitor_method_strings.join('\n')} } class ${base_class_name} { // Call a method on the visitor based on your class name accept(visitor) { throw Error(${"`accept method not implemented on ${this.constructor.name}`"}); } } ${classStrings.join('\n\n')} return {Visitor, ${classNames.join(', ')}}; }`; }; return defineAst; }36:Tbba,Expr = { // GENERATED - DO NOT MANUALLY EDIT! // To update it, modify the defineAst below and manually copy/paste its output into the next cell. class Visitor { visit_AssignExpr() { throw Error( `visit method "visit_AssignExpr" not implemented on ${this.constructor.name}` ); } visit_BinaryExpr() { throw Error( `visit method "visit_BinaryExpr" not implemented on ${this.constructor.name}` ); } visit_GroupingExpr() { throw Error( `visit method "visit_GroupingExpr" not implemented on ${this.constructor.name}` ); } visit_LiteralExpr() { throw Error( `visit method "visit_LiteralExpr" not implemented on ${this.constructor.name}` ); } visit_LogicalExpr() { throw Error( `visit method "visit_LogicalExpr" not implemented on ${this.constructor.name}` ); } visit_UnaryExpr() { throw Error( `visit method "visit_UnaryExpr" not implemented on ${this.constructor.name}` ); } visit_VariableExpr() { throw Error( `visit method "visit_VariableExpr" not implemented on ${this.constructor.name}` ); } } class Expr { // Call a method on the visitor based on your class name accept(visitor) { throw Error(`accept method not implemented on ${this.constructor.name}`); } } class Assign extends Expr { constructor(name, value) { super(); this.name = name; this.value = value; } accept(visitor) { return visitor.visit_AssignExpr(this); } } class Binary extends Expr { constructor(left, operator, right) { super(); this.left = left; this.operator = operator; this.right = right; } accept(visitor) { return visitor.visit_BinaryExpr(this); } } class Grouping extends Expr { constructor(expression) { super(); this.expression = expression; } accept(visitor) { return visitor.visit_GroupingExpr(this); } } class Literal extends Expr { constructor(value) { super(); this.value = value; } accept(visitor) { return visitor.visit_LiteralExpr(this); } } class Logical extends Expr { constructor(left, operator, right) { super(); this.left = left; this.operator = operator; this.right = right; } accept(visitor) { return visitor.visit_LogicalExpr(this); } } class Unary extends Expr { constructor(operator, right) { super(); this.operator = operator; this.right = right; } accept(visitor) { return visitor.visit_UnaryExpr(this); } } class Variable extends Expr { constructor(name) { super(); this.name = name; } accept(visitor) { return visitor.visit_VariableExpr(this); } } return { Visitor, Assign, Binary, Grouping, Literal, Logical, Unary, Variable }; }37:Tbeb,Stmt = { // GENERATED - DO NOT MANUALLY EDIT! // To update it, modify the defineAst below and manually copy/paste its output into the next cell. class Visitor { visit_BlockStmt() { throw Error( `visit method "visit_BlockStmt" not implemented on ${this.constructor.name}` ); } visit_ExpressionStmt() { throw Error( `visit method "visit_ExpressionStmt" not implemented on ${this.constructor.name}` ); } visit_ForStmt() { throw Error( `visit method "visit_ForStmt" not implemented on ${this.constructor.name}` ); } visit_IfStmt() { throw Error( `visit method "visit_IfStmt" not implemented on ${this.constructor.name}` ); } visit_PrintStmt() { throw Error( `visit method "visit_PrintStmt" not implemented on ${this.constructor.name}` ); } visit_VarStmt() { throw Error( `visit method "visit_VarStmt" not implemented on ${this.constructor.name}` ); } visit_WhileStmt() { throw Error( `visit method "visit_WhileStmt" not implemented on ${this.constructor.name}` ); } } class Stmt { // Call a method on the visitor based on your class name accept(visitor) { throw Error(`accept method not implemented on ${this.constructor.name}`); } } class Block extends Stmt { constructor(statements) { super(); this.statements = statements; } accept(visitor) { return visitor.visit_BlockStmt(this); } } class Expression extends Stmt { constructor(expression) { super(); this.expression = expression; } accept(visitor) { return visitor.visit_ExpressionStmt(this); } } class For extends Stmt { constructor(initializer, condition, increment, body) { super(); this.initializer = initializer; this.condition = condition; this.increment = increment; this.body = body; } accept(visitor) { return visitor.visit_ForStmt(this); } } class If extends Stmt { constructor(condition, thenBranch, elseBranch) { super(); this.condition = condition; this.thenBranch = thenBranch; this.elseBranch = elseBranch; } accept(visitor) { return visitor.visit_IfStmt(this); } } class Print extends Stmt { constructor(expression) { super(); this.expression = expression; } accept(visitor) { return visitor.visit_PrintStmt(this); } } class Var extends Stmt { constructor(name, initializer) { super(); this.name = name; this.initializer = initializer; } accept(visitor) { return visitor.visit_VarStmt(this); } } class While extends Stmt { constructor(condition, body) { super(); this.condition = condition; this.body = body; } accept(visitor) { return visitor.visit_WhileStmt(this); } } return { Visitor, Block, Expression, For, If, Print, Var, While }; }38:T2031,class Parser { constructor(tokens) { this.tokens = tokens; this.current = 0; } parse() { const statements = []; while (!this.isAtEnd()) { statements.push(this.declaration()); } return statements; } parseExpr() { const expr = this.expression(); if (!this.isAtEnd()) { this.error(this.peek(), 'could parse rest of tokens'); } return expr; } declaration() { if (this.match(TokenType.VAR)) return this.varDeclaration(); return this.statement(); } varDeclaration() { const name = this.consume(TokenType.IDENTIFIER, "Expected variable name"); let init = null; if (this.match(TokenType.EQUAL)) { init = this.expression(); } this.consume( TokenType.SEMICOLON, "Expected ';' after variable declaration" ); return new Stmt.Var(name, init); } statement() { if (this.check(TokenType.IF)) return this.ifStatement(); if (this.check(TokenType.WHILE)) return this.whileStatement(); if (this.check(TokenType.FOR)) return this.forStatement(); if (this.check(TokenType.PRINT)) return this.printStatement(); if (this.check(TokenType.LEFT_BRACE)) return this.block(); return this.expressionStatement(); } block() { this.consume( TokenType.LEFT_BRACE, "logic error: blockStatement called when next token was not LEFT_BRACE" ); const statements = []; while (!this.check(TokenType.RIGHT_BRACE) && !this.isAtEnd()) { statements.push(this.declaration()); } this.consume(TokenType.RIGHT_BRACE); return new Stmt.Block(statements); } printStatement() { this.consume( TokenType.PRINT, "logic error: printStatement called when next token was not PRINT" ); const value = this.expression(); this.consume(TokenType.SEMICOLON, "Expected ';' after value."); return new Stmt.Print(value); } ifStatement() { this.consume( TokenType.IF, "logic error: ifStatement called when next token was not PRINT" ); this.consume(TokenType.LEFT_PAREN, "expected '(' after 'if'"); const condition = this.expression(); this.consume(TokenType.RIGHT_PAREN, "expected ')' after 'if'"); const thenBranch = this.statement(); let elseBranch; if (this.match(TokenType.ELSE)) { elseBranch = this.statement(); } return new Stmt.If(condition, thenBranch, elseBranch); } whileStatement() { this.consume( TokenType.WHILE, "logic error: ifStatement called when next token was not PRINT" ); this.consume(TokenType.LEFT_PAREN, "expected '(' after 'while'"); const condition = this.expression(); this.consume(TokenType.RIGHT_PAREN, "expected ')' after 'while'"); const body = this.statement(); return new Stmt.While(condition, body); } forStatement() { this.consume( TokenType.FOR, "logic error: ifStatement called when next token was not PRINT" ); this.consume(TokenType.LEFT_PAREN, "expected '(' after 'while'"); let initializer; if (this.match(TokenType.SEMICOLON)) { // no initializer } else if (this.match(TokenType.VAR)) { initializer = this.varDeclaration(); } else { initializer = this.expressionStatement(); } let condition; if (!this.check(TokenType.SEMICOLON)) { condition = this.expression(); } else { condition = new Expr.Literal(true); } this.consume(TokenType.SEMICOLON, "Expected ':' after loop condition."); let increment = null; if (!this.check(TokenType.RIGHT_PAREN)) { increment = this.expression(); } this.consume(TokenType.RIGHT_PAREN, "Expected ')' after for clauses."); const body = this.statement(); return new Stmt.Block( [].concat(initializer ? [initializer] : [], [ new Stmt.While( condition, new Stmt.Block([].concat([body], increment ? [increment] : [])) ) ]) ); } expressionStatement() { const expr = this.expression(); this.consume(TokenType.SEMICOLON, "Expected ';' after expression."); return new Stmt.Expression(expr); } expression() { return this.assignment(); } assignment() { const expr = this.or(); if (this.match(TokenType.EQUAL)) { const equals = this.previous(); const value = this.assignment(); if (expr instanceof Expr.Variable) { return new Expr.Assign(expr.name, value); } error(equals, "Invalid assignment target."); } return expr; } or() { let expr = this.and(); while (this.match(TokenType.OR)) { const operator = this.previous(); const right = this.and(); expr = new Expr.Logical(expr, operator, right); } return expr; } and() { let expr = this.equality(); while (this.match(TokenType.AND)) { const operator = this.previous(); const right = this.equality(); expr = new Expr.Logical(expr, operator, right); } return expr; } equality() { let expr = this.comparison(); while (this.match(TokenType.BANG_EQUAL, TokenType.EQUAL_EQUAL)) { const operator = this.previous(); const right = this.comparison(); expr = new Expr.Binary(expr, operator, right); } return expr; } comparison() { let expr = this.addition(); while ( this.match( TokenType.GREATER, TokenType.GREATER_EQUAL, TokenType.LESS, TokenType.LESS_EQUAL ) ) { const operator = this.previous(); const right = this.addition(); expr = new Expr.Binary(expr, operator, right); } return expr; } addition() { let expr = this.multiplication(); while (this.match(TokenType.MINUS, TokenType.PLUS)) { const operator = this.previous(); const right = this.multiplication(); expr = new Expr.Binary(expr, operator, right); } return expr; } multiplication() { let expr = this.unary(); while (this.match(TokenType.SLASH, TokenType.STAR)) { const operator = this.previous(); const right = this.unary(); expr = new Expr.Binary(expr, operator, right); } return expr; } unary() { if (this.match(TokenType.BANG, TokenType.MINUS)) { const operator = this.previous(); const right = this.unary(); return new Expr.Unary(operator, right); } return this.primary(); } primary() { if (this.match(TokenType.FALSE)) return new Expr.Literal(false); if (this.match(TokenType.TRUE)) return new Expr.Literal(true); if (this.match(TokenType.NIL)) return new Expr.Literal(null); if (this.match(TokenType.NUMBER, TokenType.STRING)) { return new Expr.Literal(this.previous().literal); } if (this.match(TokenType.IDENTIFIER)) { return new Expr.Variable(this.previous()); } if (this.match(TokenType.LEFT_PAREN)) { const expr = this.expression(); this.consume(TokenType.RIGHT_PAREN, "expected ')' after expression."); return new Expr.Grouping(expr); } if (this.match(TokenType.LET)) { const variable = this.consume(TokenType.IDENTIFIER); this.consume(TokenType.EQUAL); const init = this.expression(); this.consume(TokenType.IN); const expr = this.expression(); console.log(variable, init, expr); } this.error(this.peek(), "expected expression"); } match(...token_types) { for (let token_type of token_types) { if (this.check(token_type)) { this.advance(); return true; } } return false; } check(token_type) { if (this.isAtEnd()) { return false; } return this.peek().type === token_type; } advance() { if (!this.isAtEnd()) { this.current += 1; } return this.previous(); } isAtEnd() { return this.peek().type === TokenType.EOF; } peek() { return this.tokens[this.current]; } previous() { return this.tokens[this.current - 1]; } consume(token_type, message) { if (this.check(token_type)) { return this.advance(); } this.error(this.peek(), message); } error(token, message) { throw new ParseError(token, message); } }39:T610,class ASTPrinter extends Expr.Visitor { pprintStmt(stmt) { return stmt.accept(this); } pprintExpr(expr) { return expr.accept(this); } visit_BlockStmt(stmt) { return `{${stmt.statements.map(x => x.accept(this)).join('; ')}}`; } visit_IfStmt(stmt) { return `(if ${stmt.condition.accept(this)} then ${stmt.thenBranch.accept( this )}${stmt.elseBranch ? ` else ${stmt.elseBranch.accept(this)})` : ')'}`; } visit_WhileStmt(stmt) { return `(while ${stmt.condition.accept(this)} do ${stmt.body.accept( this )})}`; } visit_ExpressionStmt(stmt) { return `${stmt.expression.accept(this)}`; } visit_PrintStmt(stmt) { return `(print ${stmt.expression.accept(this)})`; } visit_VariableExpr(expr) { return `(lookup ${expr.name.lexeme})`; } visit_AssignExpr(expr) { return `(${expr.name.lexeme} = ${expr.value.accept(this)})`; } visit_BinaryExpr(expr) { return `(${expr.operator.lexeme} ${expr.left.accept( this )} ${expr.right.accept(this)})`; } visit_LogicalExpr(expr) { return `(${expr.operator.lexeme} ${expr.left.accept( this )} ${expr.right.accept(this)})`; } visit_GroupingExpr(expr) { return `(group ${expr.expression.accept(this)})`; } visit_LiteralExpr(expr) { return expr.value === null ? 'nil' : expr.value; } visit_UnaryExpr(expr) { return `({expr.operator.lexeme} {expr.right.accept(this)})`; } visit_VarStmt(stmt) { return `(define ${stmt.name.lexeme} = ${stmt.initializer.accept(this)})`; } }3a:Tfce,class ASTInterpreter extends AstVisitor { constructor() { super(); this.env = new Environment(); } interpret(stmts) { this.outputs = []; for (let stmt of stmts) { this.execute(stmt); } return this.outputs; } execute(stmt) { return stmt.accept(this); } evaluate(expr) { return expr.accept(this); } executeBlock(stmts, env) { const prevEnv = this.env; this.env = env; try { for (let stmt of stmts) { this.execute(stmt); } } finally { this.env = prevEnv; } } visit_IfStmt(stmt) { if (this.isTruthy(this.evaluate(stmt.condition))) { this.execute(stmt.thenBranch); } else if (stmt.elseBranch) { this.execute(stmt.elseBranch); } } visit_WhileStmt(stmt) { while (this.isTruthy(this.evaluate(stmt.condition))) { this.execute(stmt.body); } } visit_BlockStmt(stmt) { this.executeBlock(stmt.statements, new Environment(this.env)); } visit_VarStmt(stmt) { let value = null; if (stmt.initializer) { value = this.evaluate(stmt.initializer); } this.env.define(stmt.name.lexeme, value); } visit_PrintStmt(stmt) { const value = this.evaluate(stmt.expression); this.outputs.push(this.stringify(value)); } visit_ExpressionStmt(stmt) { this.evaluate(stmt.expression); } visit_AssignExpr(expr) { const value = this.evaluate(expr.value); this.env.assign(expr.name, value); return value; } visit_VariableExpr(expr) { return this.env.get(expr.name); } visit_LogicalExpr(expr) { const left = expr.left.accept(this); if (expr.operator.type == TokenType.OR) { if (this.isTruthy(left)) return left; } else { if (!this.isTruthy(left)) return left; } return this.evaluate(expr.right); } visit_BinaryExpr(expr) { const [left, right] = [this.evaluate(expr.left), this.evaluate(expr.right)]; switch (expr.operator.type) { case TokenType.PLUS: if (typeof left === "string" && typeof right === "string") { return left + right; } else if (typeof left === "number" && typeof right === "number") { return left + right; } else { throw new LoxRuntimeError( expr.operator, `+ expects two strings or two numbers` ); } case TokenType.MINUS: return this.assertNumber(left) - this.assertNumber(right); case TokenType.SLASH: return this.assertNumber(left) / this.assertNumber(right); case TokenType.STAR: return this.assertNumber(left) * this.assertNumber(right); case TokenType.GREATER: return this.assertNumber(left) > this.assertNumber(right); case TokenType.GREATER_EQUAL: return this.assertNumber(left) >= this.assertNumber(right); case TokenType.LESS: return this.assertNumber(left) < this.assertNumber(right); case TokenType.LESS_EQUAL: return this.assertNumber(left) <= this.assertNumber(right); case TokenType.BANG_EQUAL: return !this.isEqual(left, right); case TokenType.EQUAL_EQUAL: return this.isEqual(left, right); } } visit_GroupingExpr(expr) { return this.evaluate(expr.expression); } visit_LiteralExpr(expr) { return expr.value; } visit_UnaryExpr(expr) { const right = this.evaluate(expr.right); switch (expr.operator.type) { case TokenType.MINUS: { return -right; break; } case TokenType.BANG: { return !this.isTruthy(right); } default: { throw Error(`Unimplemented unary operator: ${expr.operator.type}`); } } } evaluate(expr) { return expr.accept(this); } isTruthy(expr) { return !!expr; } isEqual(e1, e2) { return e1 === e2; } assertNumber(num, token) { if (typeof num !== "number") { throw new LoxRuntimeError(token, `expected number, not ${num}`); } return num; } stringify(value) { return '' + value; } }3b:T78c,chart = data => { let root = d3.hierarchy(data, children); root.dx = 10; root.dy = 800 / root.height + 1; root = d3.tree().nodeSize([root.dx, root.dy])(root); const svg = d3 .select(DOM.svg(500, 500)) .style("background", "white") .style("font", "10px sans-serif"); const g = svg.append("g"); const link = g .append("g") .attr("fill", "none") .attr("stroke", "#555") .attr("stroke-opacity", 0.4) .attr("stroke-width", 1.5) .selectAll("path") .data(root.links()) .enter() .append("path") .attr( "d", d => ` M${d.target.y},${d.target.x} C${d.source.y + root.dy / 2},${d.target.x} ${d.source.y + root.dy / 2},${d.source.x} ${d.source.y},${d.source.x} ` ); const node = g .append("g") .attr("stroke-linejoin", "round") .attr("stroke-width", 3) .selectAll("g") .data(root.descendants().reverse()) .enter() .append("g") .attr("transform", d => `translate(${d.y},${d.x})`); node .append("circle") .attr("fill", d => (d.children ? 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Ballinger","avatar_url":"https://avatars-next.observableusercontent.com/fdc16c011489d914c05fa5992a7992413727fc69e4f73671ec38919807f547e7","tier":"starter_2024"},"version":1302,"publish_version":1302,"role":null,"authored":false,"authors":[{"type":"individual","id":"4c607438c80998ad","login":"ballingt","name":"Thomas Ballinger","avatar_url":"https://avatars-next.observableusercontent.com/fdc16c011489d914c05fa5992a7992413727fc69e4f73671ec38919807f547e7","tier":null}],"members":[{"type":"individual","id":"4c607438c80998ad","login":"ballingt","name":"Thomas Ballinger","avatar_url":"https://avatars-next.observableusercontent.com/fdc16c011489d914c05fa5992a7992413727fc69e4f73671ec38919807f547e7","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":2,"collection":null,"type":"notebook","body":{"title":"JSLox as of the end of Ch 9, \"Control Flow\"","cells":[{"id":0,"value":"md`# JSLox as of the end of Ch 9, \"Control Flow\"`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":173,"value":"main(`print 1 + 12 < 23.4;\n print 2 + 3;`)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":212,"value":"md`Try it live!`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":12,"value":"codeInput()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1011,"value":"showTokens(scanTokens(input))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1077,"value":"showAST(parse(scanTokens(input)))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":25,"value":"run(input)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":238,"value":"md`## main`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":3,"value":"function main() {\n const args = [...arguments];\n if (args.length > 1) {\n return 'Pass a string to main';\n } else if (args.length == 1) {\n return run(args[0]);\n } else if (args.length == 0) {\n return 'to run prompt, use input box';\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":33,"value":"run = src => {\n const tokens = scanTokens(src);\n const stmts = parse(tokens);\n return interpret(stmts);\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":50,"value":"error = (line, where, message = '') => {\n console.log('running error with', line, where, message);\n return `[line ${line}] Error \"${where}\": ${message}`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":241,"value":"md`## scanning`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":789,"value":"codeInput()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":987,"value":"showTokens(scanTokens(input))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":85,"value":"scanTokens(input)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":57,"value":"$33","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":75,"value":"class Token {\n constructor(type, lexeme, literal, line) {\n this.type = type;\n this.lexeme = lexeme;\n this.literal = literal;\n this.line = line;\n }\n\n toString() {\n return `${this.type} ${this.lexeme} at line ${this.line}`;\n }\n toValue() {\n return this.toString();\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":129,"value":"reportError = (line, msg) => {\n console.error(error(line, '?', msg));\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":158,"value":"keywords = ({\n and: TokenType.AND,\n class: TokenType.CLASS,\n else: TokenType.ELSE,\n false: TokenType.FALSE,\n for: TokenType.FOR,\n fun: TokenType.FUN,\n if: TokenType.IF,\n nil: TokenType.NIL,\n or: TokenType.OR,\n print: TokenType.PRINT,\n return: TokenType.RETURN,\n super: TokenType.SUPER,\n this: TokenType.THIS,\n true: TokenType.TRUE,\n var: TokenType.VAR,\n while: TokenType.WHILE,\n let: TokenType.LET,\n in: TokenType.IN\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":117,"value":"$34","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":199,"value":"jsloxAST = strings => {\n return parse(scanTokens(strings[0]));\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":244,"value":"md`## ast nodes\n\nThis is the metaprogramming bit`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":258,"value":"$35","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":730,"value":"copyableCode(\n defineAst(\"Expr\", [\n \"Assign : name, value\",\n \"Binary : left, operator, right\",\n \"Grouping : expression\",\n \"Literal : value\",\n \"Logical : left, operator, right\",\n \"Unary : operator, right\",\n \"Variable : name\"\n ])\n)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":323,"value":"$36","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":720,"value":"copyableCode(\n defineAst(\"Stmt\", [\n \"Block : statements\",\n \"Expression : expression\",\n \"For : initializer, condition, increment, body\",\n \"If : condition, thenBranch, elseBranch\",\n \"Print : expression\",\n \"Var : name, initializer\",\n \"While : condition, body\"\n ])\n)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":717,"value":"$37","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":346,"value":"md`### visitors\n\nLet's combine our visitor classes into one class, AstVisitor:`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":827,"value":"AstVisitor = {\n class AstVisitor {}\n\n const methodsToAdd = {};\n for (let visitorClass of [Expr.Visitor, Stmt.Visitor]) {\n Object.getOwnPropertyNames(visitorClass.prototype).map(name => {\n methodsToAdd[name] = visitorClass.prototype[name];\n });\n }\n\n Object.assign(AstVisitor.prototype, methodsToAdd);\n\n return AstVisitor;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":389,"value":"md`# Parsing`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1072,"value":"codeInput()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1070,"value":"showAST(parse(scanTokens(input)))","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":417,"value":"parse = tokens => {\n const p = new Parser(tokens);\n return p.parse();\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":890,"value":"parseExpr = tokens => {\n const p = new Parser(tokens);\n return p.parseExpr();\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":888,"value":"parse","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":395,"value":"class ParseError extends Error {\n constructor(token, ...args) {\n super(...args);\n this.token = token;\n }\n toString() {\n return `${this.message} at ${this.token}`;\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":394,"value":"$38","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":744,"value":"md`# Pretty-Printing`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":793,"value":"codeInput()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":471,"value":"pprint(parse(scanTokens(input)))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":467,"value":"pprint = stmtsOrTree => {\n if (stmtsOrTree.length) {\n const stmts = stmtsOrTree;\n const stmtPPrints = [];\n for (let stmt of stmts) {\n stmtPPrints.push(new ASTPrinter().pprintStmt(stmt));\n }\n return `[\\n${stmtPPrints.join('\\n')}\\n]`;\n } else {\n const tree = stmtsOrTree;\n new ASTPrinter().pprintExpr(tree);\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":366,"value":"$39","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":535,"value":"md`# Interpreting`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":927,"value":"codeInput()","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":582,"value":"evaluate(parseExpr(scanTokens('1 + 1')))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":899,"value":"interpret(parse(scanTokens(input)))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":922,"value":"interpret = stmts => new ASTInterpreter().interpret(stmts)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":901,"value":"execute = stmt => new ASTInterpreter().execute(stmt)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":574,"value":"evaluate = ast => new ASTInterpreter().evaluate(ast)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":543,"value":"$3a","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":544,"value":"class LoxRuntimeError extends Error {\n constructor(token, ...args) {\n super(...args);\n this.token = token;\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":588,"value":"jslox = strings => {\n return evaluate(parse(scanTokens(strings[0])));\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1150,"value":"md`### Environment`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1157,"value":"class Environment {\n constructor(enclosing) {\n this.enclosing = enclosing;\n this.values = new Map();\n }\n get(name) {\n if (this.values.has(name.lexeme)) {\n const val = this.values.get(name.lexeme);\n return val;\n }\n\n if (this.enclosing) return this.enclosing.get(name);\n\n throw new LoxRuntimeError(\n name.lexeme,\n `Undefined variable ${name.lexeme})`\n );\n }\n\n assign(name, value) {\n if (this.values.has(name.lexeme)) {\n this.values.set(name.lexeme, value);\n return;\n }\n\n if (this.enclosing) return this.enclosing.assign(name, value);\n\n throw new LoxRuntimeError(\n name.lexeme,\n `Undefined variable ${name.lexeme})`\n );\n }\n\n define(name, value) {\n this.values.set(name, value);\n }\n\n toString() {\n return `Env(${this.Map})`;\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":759,"value":"md`### Appendix: Other code needed for the notebook`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":715,"value":"import { copyableCode } from '@ballingt/copy-this-code'","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":764,"value":"import { bind, View } from '@ballingt/synchronized-views-for-text'","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":765,"value":"viewof input = new View(`var i = 0;\nwhile (i<3) {\n print i;\n i = i + 1;\n}`)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":772,"value":"codeInput = () =>\n bind(\n html``,\n viewof input\n )","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1114,"value":"md`#### Token viz`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":981,"value":"showTokens(scanTokens('print 1 + 2 * 3; print 4 * 3;'))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":950,"value":"showTokens = tokens => {\n const divs = tokens.map(\n ({\n type,\n lexeme,\n line\n }) => html`

\n${type.name}\n

`\n );\n const container = html`

`;\n divs.forEach(x => container.appendChild(x));\n return container;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1100,"value":"md`#### Tree Viz\n\nThis should be it's own notebook eventually, currently it relies on Tokens, Expr nodes etc. which are defined here.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1060,"value":"showAST(parse(scanTokens('print 1 + 2 * 3; print 4 * 3;')))","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1040,"value":"showAST = ast => {\n if (Array.isArray(ast)) {\n return chart(new Program(ast));\n } else {\n return chart(ast);\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1090,"value":"class Program {\n constructor(statements) {\n this.statements = statements;\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1049,"value":"d3 = require(\"d3@5\")","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1050,"value":"children = node => {\n if (node instanceof Token) {\n return null;\n }\n if (node instanceof Expr.Literal) {\n return null;\n }\n const children = Object.getOwnPropertyNames(node)\n .filter(name => name !== 'role' && name !== 'length')\n .map(name => {\n let child = node[name];\n if (Array.isArray(child)) {\n child = Object.assign({ role: 'statements' }, child);\n }\n if (!Array.isArray(child) && typeof child !== 'number') {\n child.role = name;\n }\n return child;\n });\n return children;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":1054,"value":"$3b","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W3c","stdlib":"1","titling":"auto"}} 32:"$31:body"