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function parseAdd(expression: string): Expression {    const content = expression.slice("(add ".length, -1);    const list = parseList("(" + content + ")");    // console.log(list);    if (Array.isArray(list) && list.length !== 2) {        throw Error("Invalid expression");    }    return buildExpression(["add", ...list]);}function parseLet(expression: string): Expression {    const content = expression.slice("(let ".length, -1);    const list = parseList("(" + content + ")");    // console.log(list);    if (Array.isArray(list) && list.length < 3) {        throw Error("Invalid expression");    }    return buildExpression(["let", ...list]);}
function parseMult(expression: string): Expression {    const content = expression.slice("(mult ".length, -1);    const list = parseList("(" + content + ")");    // console.log(list);    if (Array.isArray(list) && list.length !== 2) {        throw Error("Invalid expression");    }    return buildExpression(["mult", ...list]);}function buildExpression(list: string | number | ListArray): Expression {    // console.log(list);    if (Array.isArray(list) && list[0] === "let") {        const variables = list.slice(1, -1).map(buildExpression);        // console.log(variables);        const declarations: VariableDeclarator[] = Array(variables.length / 2)            .fill(0)            .map((_, i) => {                const ident = variables[i * 2];                if (ident.type !== "Identifier") {                    throw Error("Invalid identifier");                }                return {                    type: "VariableDeclarator",                    id: ident,                    init: variables[i * 2 + 1],                };            });        return {            type: "LetExpression",
            declarations: declarations,            return: {                type: "ReturnStatement",                argument: buildExpression(list[list.length - 1]),            },        };    }    if (typeof list === "string") {        return parseIdentifier(list);    }    if (typeof list === "number") {        return parseNumeric(list);    }
    if (Array.isArray(list) && list.length == 0) {        throw Error("Invalid expression");    }    if (Array.isArray(list) && list[0] === "mult") {        return {            type: "MultExpression",
            left: buildExpression(list[1]),            right: buildExpression(list[2]),        };    }    if (Array.isArray(list) && list[0] === "add") {        return {            type: "AddExpression",
            left: buildExpression(list[1]),            right: buildExpression(list[2]),        };    }    throw Error("Not implemented");}export type ListArray = Array<ListArray | string | number>;function parseList(expression: string): ListArray {    return JSON.parse(        expression            .replaceAll("(", "[")            .replaceAll(")", "]")            .replaceAll(" ", ",")            .replaceAll(/[a-z]([a-z]|\d)*/g, (a) => '"' + a + '"'),    );}
function parseNumeric(expression: string | number): Expression {    return { type: "NumericLiteral", value: Number(expression) };}
function evaluate(expression: string): number {    // console.log(expression);    const ast = parse(expression);    // console.log(ast);    return calculate(ast, new ScopeList());}function parse(expression: string): Expression {    if (expression.length === 0) {        throw new Error("Empty expression");    }
    if (/^\d+$/g.test(expression)) return parseNumeric(expression);    if (expression.startsWith("(add ") && expression.endsWith(")")) {        return parseAdd(expression);    }    if (expression.startsWith("(mult ") && expression.endsWith(")")) {        return parseMult(expression);    }    if (expression.startsWith("(let ") && expression.endsWith(")")) {        return parseLet(expression);    }    if (/^[a-z]([a-z]|\d)*$/g.test(expression)) {        return parseIdentifier(expression);    }    throw new Error("Unsupported expression");}function parseIdentifier(expression: string): Expression {    return { type: "Identifier", name: expression };}
function calculate(expression: Expression, scope: ScopeList): number {    // console.log(expression, scope);    switch (expression.type) {        case "Identifier":            return getVariable(scope, expression.name);        case "NumericLiteral":            return expression.value;        case "MultExpression":            return (                calculate(expression.left, scope) *                calculate(expression.right, scope)            );        case "AddExpression":            return (                calculate(expression.left, scope) +                calculate(expression.right, scope)            );        case "LetExpression": {            const newScope = new ScopeList(new Map(), scope);            expression.declarations.forEach((declaration) => {                newScope.variables.set(                    declaration.id.name,                    calculate(declaration.init, newScope),                );            });            return calculate(expression.return.argument, newScope);        }    }}export type Expression =    | Identifier    | LetExpression    | NumericLiteral    | AddExpression    | MultExpression;export class ScopeList {    constructor(        public readonly variables: Map<string, number> = new Map(),        public parent: ScopeList | null | undefined = null,    ) {}}export interface VariableDeclarator {    type: "VariableDeclarator";    id: LVal;    init: Expression;}export type LVal = Identifier;export interface LetExpression {    type: "LetExpression";    declarations: Array<VariableDeclarator>;    return: ReturnStatement;}export interface NumericLiteral {    type: "NumericLiteral";    value: number;}export interface AddExpression {    type: "AddExpression";    left: Expression;    right: Expression;}export interface MultExpression {    type: "MultExpression";    left: Expression;    right: Expression;}export interface ReturnStatement {    type: "ReturnStatement";    argument: Expression;}export interface Identifier {    type: "Identifier";    name: string;}export default evaluate;export function getVariable(scope: ScopeList, name: string): number {    if (!scope.parent && !scope.variables.has(name)) {        throw Error("Variable not found:" + name);    }    const value = scope.variables.get(name);    if (scope.variables.has(name) && typeof value !== "undefined") {        return value;    }    if (scope.parent) return getVariable(scope.parent, name);    throw Error("Variable not found:" + name);}