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See issue #587. * Merge eval-ast and eval into a single conditional. * Expand macros during the apply phase, removing lots of duplicate tests, and increasing the overall consistency by allowing the macro to be computed instead of referenced by name (`((defmacro! cond (...)))` is currently illegal for example). * Print "EVAL: $ast" at the top of EVAL if DEBUG-EVAL exists in the MAL environment. * Remove macroexpand and quasiquoteexpand special forms. * Use pattern-matching style in process/step*.txt. Unresolved issues: c.2: unable to reproduce with gcc 11.12.0. elm: the directory is unchanged. groovy: sometimes fail, but not on each rebuild. nasm: fails some new soft tests, but the issue is unreproducible when running the interpreter manually. objpascal: unreproducible with fpc 3.2.2. ocaml: unreproducible with 4.11.1. perl6: unreproducible with rakudo 2021.09. Unrelated changes: Reduce diff betweens steps. Prevent defmacro! from mutating functions: c forth logo miniMAL vb. dart: fix recent errors and warnings ocaml: remove metadata from symbols. Improve the logo implementation. Encapsulate all representation in types.lg and env.lg, unwrap numbers. Replace some manual iterations with logo control structures. Reduce the diff between steps. Use native iteration in env_get and env_map Rewrite the reader with less temporary strings. Reduce the number of temporary lists (for example, reverse iteration with butlast requires O(n^2) allocations). It seems possible to remove a few exceptions: GC settings (Dockerfile), NO_SELF_HOSTING (IMPLS.yml) and step5_EXCLUDES (Makefile.impls) .
221 lines
6.7 KiB
Dart
221 lines
6.7 KiB
Dart
import 'dart:io';
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import 'core.dart';
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import 'env.dart';
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import 'printer.dart' as printer;
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import 'reader.dart' as reader;
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import 'types.dart';
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final Env replEnv = new Env();
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void setupEnv(List<String> argv) {
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ns.forEach((sym, fun) => replEnv.set(sym, fun));
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replEnv.set('eval',
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new MalBuiltin((List<MalType> args) => EVAL(args.single, replEnv)));
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replEnv.set('*ARGV*',
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new MalList(argv.map((s) => new MalString(s)).toList()));
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rep('(def! not (fn* (a) (if a false true)))');
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rep("(def! load-file "
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" (fn* (f) (eval (read-string (str \"(do \" (slurp f) \"\nnil)\")))))");
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rep("(defmacro! cond "
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" (fn* (& xs) (if (> (count xs) 0) "
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" (list 'if (first xs) "
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" (if (> (count xs) 1) "
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" (nth xs 1) "
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" (throw \"odd number of forms to cond\")) "
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" (cons 'cond (rest (rest xs)))))))");
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}
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bool starts_with(MalType ast, String sym) {
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return ast is MalList && ast.length == 2 && ast.first == new MalSymbol(sym);
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}
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MalType qq_loop(List<MalType> xs) {
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var acc = new MalList([]);
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for (var i=xs.length-1; 0<=i; i-=1) {
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if (starts_with(xs[i], "splice-unquote")) {
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acc = new MalList([new MalSymbol("concat"), (xs[i] as MalList)[1], acc]);
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} else {
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acc = new MalList([new MalSymbol("cons"), quasiquote(xs[i]), acc]);
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}
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}
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return acc;
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}
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MalType quasiquote(MalType ast) {
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if (starts_with(ast, "unquote")) {
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return (ast as MalList).elements[1];
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} else if (ast is MalList) {
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return qq_loop(ast.elements);
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} else if (ast is MalVector) {
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return new MalList([new MalSymbol("vec"), qq_loop(ast.elements)]);
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} else if (ast is MalSymbol || ast is MalHashMap) {
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return new MalList([new MalSymbol("quote"), ast]);
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} else {
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return ast;
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}
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}
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MalType READ(String x) => reader.read_str(x);
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MalType EVAL(MalType ast, Env env) {
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while (true) {
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var dbgeval = env.get("DEBUG-EVAL");
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if (dbgeval != null && !(dbgeval is MalNil)
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&& !(dbgeval is MalBool && dbgeval.value == false)) {
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stdout.writeln("EVAL: ${printer.pr_str(ast)}");
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}
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if (ast is MalSymbol) {
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var result = env.get(ast.value);
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if (result == null) {
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throw new NotFoundException(ast.value);
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}
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return result;
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} else if (ast is MalList) {
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// Exit this switch.
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} else if (ast is MalVector) {
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return new MalVector(ast.elements.map((x) => EVAL(x, env)).toList());
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} else if (ast is MalHashMap) {
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var newMap = new Map<MalType, MalType>.from(ast.value);
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for (var key in newMap.keys) {
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newMap[key] = EVAL(newMap[key], env);
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}
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return new MalHashMap(newMap);
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} else {
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return ast;
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}
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// ast is a list. todo: indent left.
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if ((ast as MalList).isEmpty) return ast;
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var list = ast as MalList;
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if (list.elements.first is MalSymbol) {
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var symbol = list.elements.first as MalSymbol;
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var args = list.elements.sublist(1);
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if (symbol.value == "def!") {
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MalSymbol key = args.first;
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MalType value = EVAL(args[1], env);
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env.set(key.value, value);
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return value;
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} else if (symbol.value == "defmacro!") {
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MalSymbol key = args.first;
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MalClosure macro = (EVAL(args[1], env) as MalClosure).clone();
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macro.isMacro = true;
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env.set(key.value, macro);
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return macro;
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} else if (symbol.value == "let*") {
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// TODO(het): If elements.length is not even, give helpful error
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Iterable<List<MalType>> pairs(List<MalType> elements) sync* {
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for (var i = 0; i < elements.length; i += 2) {
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yield [elements[i], elements[i + 1]];
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}
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}
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var newEnv = new Env(env);
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MalIterable bindings = args.first;
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for (var pair in pairs(bindings.elements)) {
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MalSymbol key = pair[0];
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MalType value = EVAL(pair[1], newEnv);
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newEnv.set(key.value, value);
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}
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ast = args[1];
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env = newEnv;
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continue;
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} else if (symbol.value == "do") {
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for (var elt in args.sublist(0, args.length - 1)) {
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EVAL(elt, env);
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}
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ast = args.last;
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continue;
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} else if (symbol.value == "if") {
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var condition = EVAL(args[0], env);
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if (condition is MalNil ||
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condition is MalBool && condition.value == false) {
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// False side of branch
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if (args.length < 3) {
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return new MalNil();
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}
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ast = args[2];
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continue;
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} else {
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// True side of branch
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ast = args[1];
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continue;
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}
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} else if (symbol.value == "fn*") {
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var params = (args[0] as MalIterable)
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.elements
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.map((e) => e as MalSymbol)
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.toList();
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return new MalClosure(
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params,
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args[1],
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env,
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(List<MalType> funcArgs) =>
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EVAL(args[1], new Env(env, params, funcArgs)));
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} else if (symbol.value == "quote") {
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return args.single;
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} else if (symbol.value == "quasiquote") {
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ast = quasiquote(args.first);
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continue;
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}
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}
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var f = EVAL(list.elements.first, env);
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if (f is MalCallable && f.isMacro) {
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ast = f.call(list.elements.sublist(1));
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continue;
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}
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var args = list.elements.sublist(1).map((x) => EVAL(x, env)).toList();
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if (f is MalBuiltin) {
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return f.call(args);
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} else if (f is MalClosure) {
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ast = f.ast;
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env = new Env(f.env, f.params, args);
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continue;
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} else {
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throw 'bad!';
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}
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}
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}
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String PRINT(MalType x) => printer.pr_str(x);
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String rep(String x) {
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return PRINT(EVAL(READ(x), replEnv));
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}
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const prompt = 'user> ';
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main(List<String> args) {
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setupEnv(args.isEmpty ? const <String>[] : args.sublist(1));
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if (args.isNotEmpty) {
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rep("(load-file \"${args.first}\")");
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return;
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}
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while (true) {
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stdout.write(prompt);
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var input = stdin.readLineSync();
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if (input == null) return;
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var output;
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try {
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output = rep(input);
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} on reader.ParseException catch (e) {
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stdout.writeln("Error: '${e.message}'");
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continue;
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} on NotFoundException catch (e) {
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stdout.writeln("Error: '${e.value}' not found");
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continue;
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} on MalException catch (e) {
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stdout.writeln("Error: ${printer.pr_str(e.value)}");
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continue;
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} on reader.NoInputException {
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continue;
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}
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stdout.writeln(output);
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}
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}
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