Implemented step 2.

src/reader-printer.ts

@@ -0,0 +1,230 @@
+import {assertEquals} from "https://deno.land/std@0.224.0/assert/assert_equals.ts";
+
+export type StringToken = { type: "string"; value: string };
+export type NumberToken = { type: "number"; value: number };
+export type BooleanToken = { type: "boolean"; value: boolean };
+export type SymToken = { type: "sym"; value: string };
+export type NilToken = { type: "nil"; value: null };
+export type ListToken = {
+    type: "list";
+    value: (
+        | StringToken
+        | NumberToken
+        | BooleanToken
+        | SymToken
+        | NilToken
+        | ListToken
+        | FunctionToken
+    )[];
+};
+
+export type FunctionToken = {type: 'function', value: (...args: any[]) => any};
+
+export type AST =
+    | NilToken
+    | StringToken
+    | NumberToken
+    | BooleanToken
+    | SymToken
+    | FunctionToken
+    | ListToken;
+
+function findStringEnd(s: string): number {
+    let idx = 1;
+    let previousChar = "";
+    for (const c of Array.from(s.substring(1))) {
+        if ('"' === c && previousChar !== "\\") {
+            return idx;
+        }
+        previousChar = c;
+        idx++;
+    }
+    throw new Error(`Syntax error.  The string ${s} never ends.`);
+}
+
+function findNextString(source: string): [string, string] {
+    const stringEnd = findStringEnd(source);
+    const ret = JSON.parse(source.substring(0, stringEnd + 1));
+    return [ret, source.substring(stringEnd + 1).trim()];
+}
+
+function findTokenEnd(source: string): number {
+    // const match = source.match(/(\s|\))/gi);
+    const re = /(\s|\))/gi;
+    const ret = source.search(re);
+    return ret !== -1 ? ret : source.length;
+}
+
+function isNumber(token: string): boolean {
+    return /^[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?$/.test(token);
+}
+
+function findNextNoneStringToken(source: string): AST {
+    const tokenEnd = findTokenEnd(source);
+    const token = source.substring(0, tokenEnd);
+
+    if (token === "nil") {
+        return { type: "nil", value: null };
+    }
+
+    if (token === "true" || token === "false") {
+        return { type: "boolean", value: token === "true" };
+    }
+    if (isNumber(token)) {
+        return { type: "number", value: JSON.parse(token) };
+    }
+    return { type: "sym", value: token };
+}
+
+function findNextToken(source: string): [AST, string] {
+    if (source.startsWith("(")) {
+        let x = source.substring(1).trim();
+        let token;
+        const lst: AST[] = [];
+        while (!x.trim().startsWith(")")) {
+            [token, x] = findNextToken(x);
+            lst.push(token);
+            x = x.trim();
+        }
+        return [{ type: "list", value: lst }, x.trim().substring(1)];
+    }
+
+    if (source.startsWith('"')) {
+        const [ret, rest] = findNextString(source);
+        return [{ type: "string", value: ret }, rest];
+    }
+
+    const tokenEnd = findTokenEnd(source);
+    const token = source.substring(0, tokenEnd);
+    return [findNextNoneStringToken(token), source.substring(tokenEnd).trim()];
+}
+
+export function readAST(source: string): AST {
+    source = source.trim();
+    const [ret, _] = findNextToken(source);
+
+    return ret;
+}
+
+export function printAST(form: AST): string {
+    if (form.type === "list") {
+        const ret = form.value.map(printAST).join(" ");
+        return `(${ret})`;
+    }
+    if (form.type === "sym") {
+        return form.value;
+    }
+    if (form.type === "nil") {
+        return "nil";
+    }
+    return JSON.stringify(form.value);
+}
+
+Deno.test("basic strings", function (): void {
+    const testCases: [string, string][] = [
+        ['"foo"', "foo"],
+        ['  "foo"  ', "foo"],
+        ['"bonjour \\"poline\\""', 'bonjour "poline"'],
+    ];
+    for (const [input, exptValue] of testCases) {
+        const expt: StringToken = { type: "string", value: exptValue };
+        assertEquals(expt, readAST(input));
+    }
+});
+
+Deno.test("basic symbols", function (): void {
+    const testCases: [string, string][] = [
+        ["foo", "foo"],
+        ["trueFalse", "trueFalse"],
+        ["nil?", "nil?"],
+    ];
+    for (const [input, exptValue] of testCases) {
+        const expt: SymToken = { type: "sym", value: exptValue };
+        assertEquals(expt, readAST(input));
+    }
+});
+
+Deno.test("basic numbers", function (): void {
+    const testCases: [string, number][] = [
+        ["567", 567],
+        ["-34", -34],
+        ["-34.5", -34.5],
+    ];
+    for (const [input, exptValue] of testCases) {
+        const expt: NumberToken = { type: "number", value: exptValue };
+        assertEquals(expt, readAST(input));
+    }
+});
+
+Deno.test("basic booleans", function (): void {
+    const testCases: [string, boolean][] = [
+        ["true", true],
+        ["false", false],
+    ];
+    for (const [input, exptValue] of testCases) {
+        const expt: BooleanToken = { type: "boolean", value: exptValue };
+        assertEquals(expt, readAST(input));
+    }
+});
+
+function numberToken(value: number): NumberToken {
+    return { type: "number", value };
+}
+
+function symToken(value: string): SymToken {
+    return { type: "sym", value };
+}
+
+function listToken(value: (NumberToken | SymToken | ListToken)[]): ListToken {
+    return { type: "list", value: value };
+}
+
+Deno.test("basic list", function (): void {
+    const input = "(add 3 4)";
+    const expt = listToken([
+        symToken("add"),
+        numberToken(3),
+        numberToken(4),
+    ]);
+    assertEquals(expt, readAST(input));
+});
+
+Deno.test("list of numbers", function (): void {
+    const input = "( 1 2 3)";
+    const expt = listToken([
+        numberToken(1),
+        numberToken(2),
+        numberToken(3),
+    ]);
+    assertEquals(expt, readAST(input));
+});
+
+Deno.test("composed list", function (): void {
+    const input = "(add (mul 4 9) (inc -5))";
+    const expt = listToken([
+        symToken("add"),
+        listToken([symToken("mul"), numberToken(4), numberToken(9)]),
+        listToken([symToken("inc"), numberToken(-5)]),
+    ]);
+    assertEquals(expt, readAST(input));
+});
+
+Deno.test("basic nil", function () {
+    const expt: NilToken = { type: "nil", value: null };
+    assertEquals(expt, readAST("nil"));
+});
+
+Deno.test("step 1 tests", function (): void {
+    const cases: [string, string][] = [
+        ["123", "123"],
+        ["  123  ", "123"],
+        ["abc", "abc"],
+        ["  abc  ", "abc"],
+        ["(123 456)", "(123 456)"],
+        ["(  123   456 789   )", "(123 456 789)"],
+        ["(  + 2   (*  3  4)  ) ", "(+ 2 (* 3 4))"],
+    ];
+    for (const [input, expt] of cases) {
+        assertEquals(expt, printAST(readAST(input)));
+    }
+});

src/step0_repl.ts

@@ -0,0 +1,25 @@
+import {readUserInputs} from "./shared.ts";
+
+function read(source: string): string {
+    return source;
+}
+
+function eval_(ast: string): string {
+    return ast;
+}
+
+function print(form: string): string {
+    return form
+}
+
+function rep(source: string): string{
+    return print(eval_(read( source)))
+}
+
+
+
+export function main(): void {
+     for(const userInput of readUserInputs()){
+         rep(userInput);
+     }
+}

src/step1_read_print.ts

@@ -0,0 +1,25 @@
+import {readUserInputs} from "./shared.ts";
+import {AST, readAST, printAST} from './reader-printer.ts';
+
+function read(source: string): AST {
+    return readAST(source);
+}
+
+function eval_(ast: AST): AST {
+    return ast;
+}
+
+function print(form: AST): string {
+    return printAST(form);
+}
+
+function rep(source: string): string {
+    return print(eval_(read(source)));
+}
+
+
+export function main(): void {
+    for (const userInput of readUserInputs()) {
+        rep(userInput);
+    }
+}

src/step2_eval.ts

@@ -0,0 +1,90 @@
+import {assertEquals} from "https://deno.land/std@0.224.0/assert/assert_equals.ts";
+import {AST, FunctionToken, printAST, readAST} from "./reader-printer.ts";
+
+type MalEnv = Map<string, FunctionToken>;
+
+function functionToken(fn: (...args: any[]) => any): FunctionToken {
+    return { type: "function", value: fn };
+}
+
+function isBoolean(v: unknown): v is boolean {
+    return v === true || v === false;
+}
+
+function isNumber(v: unknown): v is number {
+    return typeof v === "number" && isFinite(v);
+}
+
+function isString(v: unknown): v is string {
+    return typeof v === "string" || v instanceof String;
+}
+
+class REPL {
+    private readonly env: MalEnv;
+
+    constructor(env: MalEnv) {
+        this.env = env;
+    }
+
+    static mathRepl(): REPL {
+        const mathFunctions = new Map<string, FunctionToken>();
+        mathFunctions.set("+", functionToken((a, b) => a + b));
+        mathFunctions.set("-", functionToken((a, b) => a - b));
+        mathFunctions.set("*", functionToken((a, b) => a * b));
+        mathFunctions.set("/", functionToken((a, b) => a / b));
+
+        return new REPL(mathFunctions);
+    }
+
+    read(source: string): AST {
+        return readAST(source);
+    }
+
+    cast(value: unknown): AST {
+        if (value === true || value === false) {
+            return { type: "boolean", value: value };
+        }
+        if (isBoolean(value)) {
+            return { type: "boolean", value: value };
+        }
+        if (isString(value)) {
+            return { type: "string", value: value };
+        }
+        if (isNumber(value)) {
+            return { type: "number", value: value };
+        }
+        throw new Error(`Unknown return type from functon: ${value}`);
+    }
+
+    eval_(ast: AST): AST {
+        if (ast.type === "list") {
+            const fn = this.eval_(ast.value[0]) as FunctionToken;
+            const ret = fn.value(
+                ...ast.value.slice(1).map((n) => this.eval_(n).value),
+            );
+            return this.cast(ret);
+        }
+        if (ast.type === "sym") {
+            const ret = this.env.get(ast.value);
+            if (ret === undefined) {
+                throw new Error(`Unknown reference ${ast.value}`);
+            }
+            return ret;
+        }
+        return ast;
+    }
+
+    print(form: AST): string {
+        return printAST(form);
+    }
+
+    rep(source: string): string {
+        return this.print(this.eval_(this.read(source)));
+    }
+}
+
+Deno.test("basic", function (): void {
+    const repl = REPL.mathRepl();
+    assertEquals(repl.rep("(+ 1 1)"), "2");
+    assertEquals(repl.rep("(+ 2 (* 3 4))"), "14");
+});