mal/impls/ts/step7_quote.ts

import { readline } from "./node_readline";

import { Node, MalType, MalString, MalNil, MalList, MalVector, MalHashMap, MalSymbol, MalFunction, isAST, isSeq } from "./types";
import { Env } from "./env";
import * as core from "./core";
import { readStr } from "./reader";
import { prStr } from "./printer";

// READ
function read(str: string): MalType {
    return readStr(str);
}

function starts_with(lst: MalType[], sym: string): boolean {
    if (lst.length == 2) {
        let a0 = lst[0]
        switch (a0.type) {
            case Node.Symbol:
                return a0.v === sym;
        }
    }
    return false;
}

function qq_loop(elt: MalType, acc: MalList): MalList {
    if (elt.type == Node.List && starts_with(elt.list, "splice-unquote")) {
        return new MalList([MalSymbol.get("concat"), elt.list[1], acc]);
    } else {
        return new MalList([MalSymbol.get("cons"), quasiquote(elt), acc]);
    }
}

function qq_foldr(xs : MalType[]): MalList {
    let acc = new MalList([])
    for (let i=xs.length-1; 0<=i; i-=1) {
         acc = qq_loop(xs[i], acc)
    }
    return acc;
}

function quasiquote(ast: MalType): MalType {
    switch (ast.type) {
        case Node.Symbol:
            return new MalList([MalSymbol.get("quote"), ast]);
        case Node.HashMap:
            return new MalList([MalSymbol.get("quote"), ast]);
        case Node.List:
            if (starts_with(ast.list, "unquote")) {
                return ast.list[1];
            } else {
                return qq_foldr(ast.list);
            }
        case Node.Vector:
            return new MalList([MalSymbol.get("vec"), qq_foldr(ast.list)]);
        default:
            return ast;
    }
}

// EVAL
function evalMal(ast: MalType, env: Env): MalType {
    loop: while (true) {
    // Output a debug line if the option is enabled.
    const dbgeval : MalType | null = env.get("DEBUG-EVAL");
    if (dbgeval !== null
        && dbgeval.type !== Node.Nil
        && (dbgeval.type !== Node.Boolean || dbgeval.v))
      console.log("EVAL:", prStr(ast));
    // Deal with non-list types.
    switch (ast.type) {
        case Node.Symbol:
            const f : MalType | null = env.get(ast.v);
            if (!f) {
                throw new Error(`'${ast.v}' not found`);
            }
            return f;
        case Node.List:
            break;
        case Node.Vector:
            return new MalVector(ast.list.map(ast => evalMal(ast, env)));
        case Node.HashMap:
            const list: MalType[] = [];
            for (const [key, value] of ast.entries()) {
                list.push(key);
                list.push(evalMal(value, env));
            }
            return new MalHashMap(list);
        default:
            return ast;
        }
        if (ast.list.length === 0) {
            return ast;
        }
        const first = ast.list[0];
        switch (first.type) {
            case Node.Symbol:
                switch (first.v) {
                    case "def!": {
                        const [, key, value] = ast.list;
                        if (key.type !== Node.Symbol) {
                            throw new Error(`unexpected token type: ${key.type}, expected: symbol`);
                        }
                        if (!value) {
                            throw new Error(`unexpected syntax`);
                        }
                        return env.set(key.v, evalMal(value, env));
                    }
                    case "let*": {
                        env = new Env(env);
                        const pairs = ast.list[1];
                        if (!isSeq(pairs)) {
                            throw new Error(`unexpected token type: ${pairs.type}, expected: list or vector`);
                        }
                        for (let i = 0; i < pairs.list.length; i += 2) {
                            const key = pairs.list[i];
                            const value = pairs.list[i + 1];
                            if (key.type !== Node.Symbol) {
                                throw new Error(`unexpected token type: ${key.type}, expected: symbol`);
                            }
                            if (!key || !value) {
                                throw new Error(`unexpected syntax`);
                            }

                            env.set(key.v, evalMal(value, env));
                        }
                        ast = ast.list[2];
                        continue loop;
                    }
                    case "quote": {
                        return ast.list[1];
                    }
                    case "quasiquote": {
                        ast = quasiquote(ast.list[1]);
                        continue loop;
                    }
                    case "do": {
                        for (let i = 1; i < ast.list.length - 1; i++)
                            evalMal(ast.list[i], env);
                        ast = ast.list[ast.list.length - 1];
                        continue loop;
                    }
                    case "if": {
                        const [, cond, thenExpr, elseExrp] = ast.list;
                        const ret = evalMal(cond, env);
                        let b = true;
                        if (ret.type === Node.Boolean && !ret.v) {
                            b = false;
                        } else if (ret.type === Node.Nil) {
                            b = false;
                        }
                        if (b) {
                            ast = thenExpr;
                        } else if (elseExrp) {
                            ast = elseExrp;
                        } else {
                            ast = MalNil.instance;
                        }
                        continue loop;
                    }
                    case "fn*": {
                        const [, params, bodyAst] = ast.list;
                        if (!isSeq(params)) {
                            throw new Error(`unexpected return type: ${params.type}, expected: list or vector`);
                        }
                        const symbols = params.list.map(param => {
                            if (param.type !== Node.Symbol) {
                                throw new Error(`unexpected return type: ${param.type}, expected: symbol`);
                            }
                            return param;
                        });
                        return MalFunction.fromLisp(evalMal, env, symbols, bodyAst);
                    }
                }
        }
        const f : MalType = evalMal(first, env);
        if (f.type !== Node.Function) {
            throw new Error(`unexpected token: ${f.type}, expected: function`);
        }
        const args : Array<MalType> = ast.list.slice(1).map(x => evalMal(x, env));
        if (f.ast) {
            ast = f.ast;
            env = f.newEnv(args);
            continue loop;
        }

        return f.func(...args);
    }
}

// PRINT
function print(exp: MalType): string {
    return prStr(exp);
}

const replEnv = new Env();
function rep(str: string): string {
    return print(evalMal(read(str), replEnv));
}

// core.EXT: defined using Racket
core.ns.forEach((value, key) => {
    replEnv.set(key, value);
});
replEnv.set("eval", MalFunction.fromBootstrap(ast => {
    if (!ast) {
        throw new Error(`undefined argument`);
    }
    return evalMal(ast, replEnv);
}));
replEnv.set("*ARGV*", new MalList([]));

// core.mal: defined using the language itself
rep("(def! not (fn* (a) (if a false true)))");
rep(`(def! load-file (fn* (f) (eval (read-string (str "(do " (slurp f) "\nnil)")))))`);

if (typeof process !== "undefined" && 2 < process.argv.length) {
    replEnv.set("*ARGV*", new MalList(process.argv.slice(3).map(s => new MalString(s))));
    rep(`(load-file "${process.argv[2]}")`);
    process.exit(0);
}

while (true) {
    const line = readline("user> ");
    if (line == null) {
        break;
    }
    if (line === "") {
        continue;
    }
    try {
        console.log(rep(line));
    } catch (e) {
        if (isAST(e)) {
            console.error("Error:", prStr(e));
        } else {
            const err: Error = e;
            console.error("Error:", err.message);
        }
    }
}