1234567891011121314151617181920212223242526272829303132333435363738
import { Expression } from "./Expression.ts";
export function evaluate(ast: Expression): number {    if (ast.type === "NumericLiteral") {        return ast.value;    }    if (ast.type === "UnaryExpression") {        if (ast.operator === "-") {            return -1 * evaluate(ast.argument);        }        throw new Error(`Unary operator ${ast.operator} not supported`);    }    if (ast.type === "BinaryExpression") {        if (ast.operator === "-") {            return evaluate(ast.left) - evaluate(ast.right);        }        if (ast.operator === "*") {            return evaluate(ast.left) * evaluate(ast.right);        }        if (ast.operator === "+") {            return evaluate(ast.left) + evaluate(ast.right);        }
        if (ast.operator === "/") {            const num1 = evaluate(ast.left);            const num2 = evaluate(ast.right);            const sign = Math.sign(num2) * Math.sign(num1);            return sign * Math.floor(Math.abs(num1) / Math.abs(num2));            //整数除法        }        throw new Error(`Binary operator ${ast.operator} not supported`);    }    if (ast.type === "ParenthesizedExpression") {        return evaluate(ast.expression);    }    throw Error("not support expression");}