[jackhill/mal.git] / cpp / step9_try.cpp

#include "MAL.h"

#include "Environment.h"
#include "ReadLine.h"
#include "Types.h"

#include <iostream>
#include <memory>

malValuePtr READ(const String& input);
String PRINT(malValuePtr ast);
static void installFunctions(malEnvPtr env);

static void makeArgv(malEnvPtr env, int argc, char* argv[]);
static String safeRep(const String& input, malEnvPtr env);
static malValuePtr quasiquote(malValuePtr obj);
static malValuePtr macroExpand(malValuePtr obj, malEnvPtr env);
static void installMacros(malEnvPtr env);

static ReadLine s_readLine("~/.mal-history");

static malEnvPtr replEnv(new malEnv);

int main(int argc, char* argv[])
{
    String prompt = "user> ";
    String input;
    installCore(replEnv);
    installFunctions(replEnv);
    installMacros(replEnv);
    makeArgv(replEnv, argc - 2, argv + 2);
    if (argc > 1) {
        String filename = escape(argv[1]);
        safeRep(STRF("(load-file %s)", filename.c_str()), replEnv);
        return 0;
    }
    while (s_readLine.get(prompt, input)) {
        String out = safeRep(input, replEnv);
        if (out.length() > 0)
            std::cout << out << "\n";
    }
    return 0;
}

static String safeRep(const String& input, malEnvPtr env)
{
    try {
        return rep(input, env);
    }
    catch (malEmptyInputException&) {
        return String();
    }
    catch (String& s) {
        return s;
    };
}

static void makeArgv(malEnvPtr env, int argc, char* argv[])
{
    malValueVec* args = new malValueVec();
    for (int i = 0; i < argc; i++) {
        args->push_back(mal::string(argv[i]));
    }
    env->set("*ARGV*", mal::list(args));
}

String rep(const String& input, malEnvPtr env)
{
    return PRINT(EVAL(READ(input), env));
}

malValuePtr READ(const String& input)
{
    return readStr(input);
}

malValuePtr EVAL(malValuePtr ast, malEnvPtr env)
{
    if (!env) {
        env = replEnv;
    }
    while (1) {
        const malList* list = DYNAMIC_CAST(malList, ast);
        if (!list || (list->count() == 0)) {
            return ast->eval(env);
        }

        ast = macroExpand(ast, env);
        list = DYNAMIC_CAST(malList, ast);
        if (!list || (list->count() == 0)) {
            return ast->eval(env);
        }

        // From here on down we are evaluating a non-empty list.
        // First handle the special forms.
        if (const malSymbol* symbol = DYNAMIC_CAST(malSymbol, list->item(0))) {
            String special = symbol->value();
            int argCount = list->count() - 1;

            if (special == "def!") {
                checkArgsIs("def!", 2, argCount);
                const malSymbol* id = VALUE_CAST(malSymbol, list->item(1));
                return env->set(id->value(), EVAL(list->item(2), env));
            }

            if (special == "defmacro!") {
                checkArgsIs("defmacro!", 2, argCount);

                const malSymbol* id = VALUE_CAST(malSymbol, list->item(1));
                malValuePtr body = EVAL(list->item(2), env);
                const malLambda* lambda = VALUE_CAST(malLambda, body);
                return env->set(id->value(), mal::macro(*lambda));
            }

            if (special == "do") {
                checkArgsAtLeast("do", 1, argCount);

                for (int i = 1; i < argCount; i++) {
                    EVAL(list->item(i), env);
                }
                ast = list->item(argCount);
                continue; // TCO
            }

            if (special == "fn*") {
                checkArgsIs("fn*", 2, argCount);

                const malSequence* bindings =
                    VALUE_CAST(malSequence, list->item(1));
                StringVec params;
                for (int i = 0; i < bindings->count(); i++) {
                    const malSymbol* sym =
                        VALUE_CAST(malSymbol, bindings->item(i));
                    params.push_back(sym->value());
                }

                return mal::lambda(params, list->item(2), env);
            }

            if (special == "if") {
                checkArgsBetween("if", 2, 3, argCount);

                bool isTrue = EVAL(list->item(1), env)->isTrue();
                if (!isTrue && (argCount == 2)) {
                    return mal::nilValue();
                }
                ast = list->item(isTrue ? 2 : 3);
                continue; // TCO
            }

            if (special == "let*") {
                checkArgsIs("let*", 2, argCount);
                const malSequence* bindings =
                    VALUE_CAST(malSequence, list->item(1));
                int count = checkArgsEven("let*", bindings->count());
                malEnvPtr inner(new malEnv(env));
                for (int i = 0; i < count; i += 2) {
                    const malSymbol* var =
                        VALUE_CAST(malSymbol, bindings->item(i));
                    inner->set(var->value(), EVAL(bindings->item(i+1), inner));
                }
                ast = list->item(2);
                env = inner;
                continue; // TCO
            }

            if (special == "macroexpand") {
                checkArgsIs("macroexpand", 1, argCount);
                return macroExpand(list->item(1), env);
            }

            if (special == "quasiquote") {
                checkArgsIs("quasiquote", 1, argCount);
                ast = quasiquote(list->item(1));
                continue; // TCO
            }

            if (special == "quote") {
                checkArgsIs("quote", 1, argCount);
                return list->item(1);
            }

            if (special == "try*") {
                checkArgsIs("try*", 2, argCount);
                malValuePtr tryBody = list->item(1);
                const malList* catchBlock = VALUE_CAST(malList, list->item(2));

                checkArgsIs("catch*", 2, catchBlock->count() - 1);
                MAL_CHECK(VALUE_CAST(malSymbol,
                    catchBlock->item(0))->value() == "catch*",
                    "catch block must begin with catch*");

                // We don't need excSym at this scope, but we want to check
                // that the catch block is valid always, not just in case of
                // an exception.
                const malSymbol* excSym =
                    VALUE_CAST(malSymbol, catchBlock->item(1));

                malValuePtr excVal;

                try {
                    ast = EVAL(tryBody, env);
                }
                catch(String& s) {
                    excVal = mal::string(s);
                }
                catch (malEmptyInputException&) {
                    // Not an error, continue as if we got nil
                    ast = mal::nilValue();
                }
                catch(malValuePtr& o) {
                    excVal = o;
                };

                if (excVal) {
                    // we got some exception
                    env = malEnvPtr(new malEnv(env));
                    env->set(excSym->value(), excVal);
                    ast = catchBlock->item(2);
                }
                continue; // TCO
            }
        }

        // Now we're left with the case of a regular list to be evaluated.
        std::unique_ptr<malValueVec> items(list->evalItems(env));
        malValuePtr op = items->at(0);
        if (const malLambda* lambda = DYNAMIC_CAST(malLambda, op)) {
            ast = lambda->getBody();
            env = lambda->makeEnv(items->begin()+1, items->end());
            continue; // TCO
        }
        else {
            return APPLY(op, items->begin()+1, items->end());
        }
    }
}

String PRINT(malValuePtr ast)
{
    return ast->print(true);
}

malValuePtr APPLY(malValuePtr op, malValueIter argsBegin, malValueIter argsEnd)
{
    const malApplicable* handler = DYNAMIC_CAST(malApplicable, op);
    MAL_CHECK(handler != NULL,
              "\"%s\" is not applicable", op->print(true).c_str());

    return handler->apply(argsBegin, argsEnd);
}

static bool isSymbol(malValuePtr obj, const String& text)
{
    const malSymbol* sym = DYNAMIC_CAST(malSymbol, obj);
    return sym && (sym->value() == text);
}

static const malSequence* isPair(malValuePtr obj)
{
    const malSequence* list = DYNAMIC_CAST(malSequence, obj);
    return list && !list->isEmpty() ? list : NULL;
}

static malValuePtr quasiquote(malValuePtr obj)
{
    const malSequence* seq = isPair(obj);
    if (!seq) {
        return mal::list(mal::symbol("quote"), obj);
    }

    if (isSymbol(seq->item(0), "unquote")) {
        // (qq (uq form)) -> form
        checkArgsIs("unquote", 1, seq->count() - 1);
        return seq->item(1);
    }

    const malSequence* innerSeq = isPair(seq->item(0));
    if (innerSeq && isSymbol(innerSeq->item(0), "splice-unquote")) {
        checkArgsIs("splice-unquote", 1, innerSeq->count() - 1);
        // (qq (sq '(a b c))) -> a b c
        return mal::list(
            mal::symbol("concat"),
            innerSeq->item(1),
            quasiquote(seq->rest())
        );
    }
    else {
        // (qq (a b c)) -> (list (qq a) (qq b) (qq c))
        // (qq xs     ) -> (cons (qq (car xs)) (qq (cdr xs)))
        return mal::list(
            mal::symbol("cons"),
            quasiquote(seq->first()),
            quasiquote(seq->rest())
        );
    }
}

static const malLambda* isMacroApplication(malValuePtr obj, malEnvPtr env)
{
    if (const malSequence* seq = isPair(obj)) {
        if (malSymbol* sym = DYNAMIC_CAST(malSymbol, seq->first())) {
            if (malEnvPtr symEnv = env->find(sym->value())) {
                malValuePtr value = sym->eval(symEnv);
                if (malLambda* lambda = DYNAMIC_CAST(malLambda, value)) {
                    return lambda->isMacro() ? lambda : NULL;
                }
            }
        }
    }
    return NULL;
}

static malValuePtr macroExpand(malValuePtr obj, malEnvPtr env)
{
    while (const malLambda* macro = isMacroApplication(obj, env)) {
        const malSequence* seq = STATIC_CAST(malSequence, obj);
        obj = macro->apply(seq->begin() + 1, seq->end());
    }
    return obj;
}

static const char* macroTable[] = {
    "(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))",
    "(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))",
};

static void installMacros(malEnvPtr env)
{
    for (auto &macro : macroTable) {
        rep(macro, env);
    }
}

static const char* malFunctionTable[] = {
    "(def! list (fn* (& items) items))",
    "(def! not (fn* (cond) (if cond false true)))",
    "(def! >= (fn* (a b) (<= b a)))",
    "(def! < (fn* (a b) (not (<= b a))))",
    "(def! > (fn* (a b) (not (<= a b))))",
    "(def! load-file (fn* (filename) \
        (eval (read-string (str \"(do \" (slurp filename) \")\")))))",
    "(def! map (fn* (f xs) (if (empty? xs) xs \
        (cons (f (first xs)) (map f (rest xs))))))",
};

static void installFunctions(malEnvPtr env) {
    for (auto &function : malFunctionTable) {
        rep(function, env);
    }
}

// Added to keep the linker happy at step A
malValuePtr readline(const String& prompt)
{
    String input;
    if (s_readLine.get(prompt, input)) {
        return mal::string(input);
    }
    return mal::nilValue();
}
Commit	Line	Data
2f61492a ST	1	#include "MAL.h"
	2
	3	#include "Environment.h"
	4	#include "ReadLine.h"
	5	#include "Types.h"
	6
	7	#include <iostream>
	8	#include <memory>
	9
	10	malValuePtr READ(const String& input);
	11	String PRINT(malValuePtr ast);
	12	static void installFunctions(malEnvPtr env);
	13
	14	static void makeArgv(malEnvPtr env, int argc, char* argv[]);
2f8f48e1	15	static String safeRep(const String& input, malEnvPtr env);
2f61492a ST	16	static malValuePtr quasiquote(malValuePtr obj);
	17	static malValuePtr macroExpand(malValuePtr obj, malEnvPtr env);
	18	static void installMacros(malEnvPtr env);
	19
	20	static ReadLine s_readLine("~/.mal-history");
	21
494c1608 ST	22	static malEnvPtr replEnv(new malEnv);
494c1608 ST	23
2f61492a ST	24	int main(int argc, char* argv[])
	25	{
	26	String prompt = "user> ";
	27	String input;
2f61492a ST	28	installCore(replEnv);
	29	installFunctions(replEnv);
	30	installMacros(replEnv);
	31	makeArgv(replEnv, argc - 2, argv + 2);
	32	if (argc > 1) {
	33	String filename = escape(argv[1]);
	34	safeRep(STRF("(load-file %s)", filename.c_str()), replEnv);
	35	return 0;
	36	}
	37	while (s_readLine.get(prompt, input)) {
2f8f48e1 DM	38	String out = safeRep(input, replEnv);
	39	if (out.length() > 0)
	40	std::cout << out << "\n";
2f61492a ST	41	}
	42	return 0;
	43	}
	44
2f8f48e1	45	static String safeRep(const String& input, malEnvPtr env)
2f61492a	46	{
2f61492a	47	try {
2f8f48e1	48	return rep(input, env);
2f61492a ST	49	}
2f61492a ST	50	catch (malEmptyInputException&) {
2f8f48e1	51	return String();
2f61492a ST	52	}
2f61492a ST	53	catch (String& s) {
2f8f48e1	54	return s;
2f61492a	55	};
2f61492a ST	56	}
	57
	58	static void makeArgv(malEnvPtr env, int argc, char* argv[])
	59	{
	60	malValueVec* args = new malValueVec();
	61	for (int i = 0; i < argc; i++) {
	62	args->push_back(mal::string(argv[i]));
	63	}
	64	env->set("ARGV", mal::list(args));
	65	}
	66
	67	String rep(const String& input, malEnvPtr env)
	68	{
	69	return PRINT(EVAL(READ(input), env));
	70	}
	71
	72	malValuePtr READ(const String& input)
	73	{
	74	return readStr(input);
	75	}
	76
	77	malValuePtr EVAL(malValuePtr ast, malEnvPtr env)
	78	{
494c1608 ST	79	if (!env) {
	80	env = replEnv;
	81	}
2f61492a ST	82	while (1) {
	83	const malList* list = DYNAMIC_CAST(malList, ast);
	84	if (!list \|\| (list->count() == 0)) {
	85	return ast->eval(env);
	86	}
	87
	88	ast = macroExpand(ast, env);
	89	list = DYNAMIC_CAST(malList, ast);
	90	if (!list \|\| (list->count() == 0)) {
	91	return ast->eval(env);
	92	}
	93
	94	// From here on down we are evaluating a non-empty list.
	95	// First handle the special forms.
	96	if (const malSymbol* symbol = DYNAMIC_CAST(malSymbol, list->item(0))) {
	97	String special = symbol->value();
	98	int argCount = list->count() - 1;
	99
	100	if (special == "def!") {
	101	checkArgsIs("def!", 2, argCount);
	102	const malSymbol* id = VALUE_CAST(malSymbol, list->item(1));
	103	return env->set(id->value(), EVAL(list->item(2), env));
	104	}
	105
	106	if (special == "defmacro!") {
	107	checkArgsIs("defmacro!", 2, argCount);
	108
	109	const malSymbol* id = VALUE_CAST(malSymbol, list->item(1));
	110	malValuePtr body = EVAL(list->item(2), env);
	111	const malLambda* lambda = VALUE_CAST(malLambda, body);
	112	return env->set(id->value(), mal::macro(*lambda));
	113	}
	114
	115	if (special == "do") {
	116	checkArgsAtLeast("do", 1, argCount);
	117
	118	for (int i = 1; i < argCount; i++) {
	119	EVAL(list->item(i), env);
	120	}
	121	ast = list->item(argCount);
	122	continue; // TCO
	123	}
	124
	125	if (special == "fn*") {
	126	checkArgsIs("fn*", 2, argCount);
	127
	128	const malSequence* bindings =
	129	VALUE_CAST(malSequence, list->item(1));
	130	StringVec params;
	131	for (int i = 0; i < bindings->count(); i++) {
	132	const malSymbol* sym =
	133	VALUE_CAST(malSymbol, bindings->item(i));
	134	params.push_back(sym->value());
	135	}
	136
	137	return mal::lambda(params, list->item(2), env);
	138	}
	139
	140	if (special == "if") {
	141	checkArgsBetween("if", 2, 3, argCount);
	142
	143	bool isTrue = EVAL(list->item(1), env)->isTrue();
	144	if (!isTrue && (argCount == 2)) {
	145	return mal::nilValue();
146	}
147	ast = list->item(isTrue ? 2 : 3);
148	continue; // TCO
149	}
150
151	if (special == "let*") {
152	checkArgsIs("let*", 2, argCount);
153	const malSequence* bindings =
154	VALUE_CAST(malSequence, list->item(1));
155	int count = checkArgsEven("let*", bindings->count());
156	malEnvPtr inner(new malEnv(env));
157	for (int i = 0; i < count; i += 2) {
158	const malSymbol* var =
159	VALUE_CAST(malSymbol, bindings->item(i));
160	inner->set(var->value(), EVAL(bindings->item(i+1), inner));
161	}
162	ast = list->item(2);
163	env = inner;
164	continue; // TCO
165	}
166
167	if (special == "macroexpand") {
168	checkArgsIs("macroexpand", 1, argCount);
169	return macroExpand(list->item(1), env);
170	}
171
172	if (special == "quasiquote") {
173	checkArgsIs("quasiquote", 1, argCount);
174	ast = quasiquote(list->item(1));
175	continue; // TCO
176	}
177
178	if (special == "quote") {
179	checkArgsIs("quote", 1, argCount);
180	return list->item(1);
181	}
182
183	if (special == "try*") {
184	checkArgsIs("try*", 2, argCount);
185	malValuePtr tryBody = list->item(1);
186	const malList* catchBlock = VALUE_CAST(malList, list->item(2));
187
188	checkArgsIs("catch*", 2, catchBlock->count() - 1);
0997015d	189	MAL_CHECK(VALUE_CAST(malSymbol,
2f61492a ST	190	catchBlock->item(0))->value() == "catch*",
	191	"catch block must begin with catch*");
	192
	193	// We don't need excSym at this scope, but we want to check
	194	// that the catch block is valid always, not just in case of
	195	// an exception.
	196	const malSymbol* excSym =
	197	VALUE_CAST(malSymbol, catchBlock->item(1));
	198
	199	malValuePtr excVal;
	200
	201	try {
	202	ast = EVAL(tryBody, env);
	203	}
	204	catch(String& s) {
	205	excVal = mal::string(s);
	206	}
	207	catch (malEmptyInputException&) {
	208	// Not an error, continue as if we got nil
	209	ast = mal::nilValue();
	210	}
	211	catch(malValuePtr& o) {
	212	excVal = o;
	213	};
	214
	215	if (excVal) {
	216	// we got some exception
	217	env = malEnvPtr(new malEnv(env));
	218	env->set(excSym->value(), excVal);
	219	ast = catchBlock->item(2);
	220	}
	221	continue; // TCO
	222	}
	223	}
	224
	225	// Now we're left with the case of a regular list to be evaluated.
	226	std::unique_ptr<malValueVec> items(list->evalItems(env));
	227	malValuePtr op = items->at(0);
	228	if (const malLambda* lambda = DYNAMIC_CAST(malLambda, op)) {
	229	ast = lambda->getBody();
	230	env = lambda->makeEnv(items->begin()+1, items->end());
	231	continue; // TCO
	232	}
	233	else {
494c1608	234	return APPLY(op, items->begin()+1, items->end());
2f61492a ST	235	}
	236	}
	237	}
	238
	239	String PRINT(malValuePtr ast)
	240	{
	241	return ast->print(true);
	242	}
	243
494c1608	244	malValuePtr APPLY(malValuePtr op, malValueIter argsBegin, malValueIter argsEnd)
2f61492a ST	245	{
2f61492a ST	246	const malApplicable* handler = DYNAMIC_CAST(malApplicable, op);
0997015d ST	247	MAL_CHECK(handler != NULL,
0997015d ST	248	"\"%s\" is not applicable", op->print(true).c_str());
2f61492a	249
494c1608	250	return handler->apply(argsBegin, argsEnd);
2f61492a ST	251	}
	252
	253	static bool isSymbol(malValuePtr obj, const String& text)
	254	{
	255	const malSymbol* sym = DYNAMIC_CAST(malSymbol, obj);
	256	return sym && (sym->value() == text);
	257	}
	258
	259	static const malSequence* isPair(malValuePtr obj)
	260	{
	261	const malSequence* list = DYNAMIC_CAST(malSequence, obj);
	262	return list && !list->isEmpty() ? list : NULL;
	263	}
	264
	265	static malValuePtr quasiquote(malValuePtr obj)
	266	{
	267	const malSequence* seq = isPair(obj);
	268	if (!seq) {
	269	return mal::list(mal::symbol("quote"), obj);
	270	}
	271
	272	if (isSymbol(seq->item(0), "unquote")) {
	273	// (qq (uq form)) -> form
	274	checkArgsIs("unquote", 1, seq->count() - 1);
	275	return seq->item(1);
	276	}
	277
	278	const malSequence* innerSeq = isPair(seq->item(0));
	279	if (innerSeq && isSymbol(innerSeq->item(0), "splice-unquote")) {
	280	checkArgsIs("splice-unquote", 1, innerSeq->count() - 1);
	281	// (qq (sq '(a b c))) -> a b c
	282	return mal::list(
	283	mal::symbol("concat"),
	284	innerSeq->item(1),
	285	quasiquote(seq->rest())
	286	);
	287	}
	288	else {
	289	// (qq (a b c)) -> (list (qq a) (qq b) (qq c))
	290	// (qq xs ) -> (cons (qq (car xs)) (qq (cdr xs)))
	291	return mal::list(
	292	mal::symbol("cons"),
	293	quasiquote(seq->first()),
	294	quasiquote(seq->rest())
	295	);
	296	}
	297	}
	298
	299	static const malLambda* isMacroApplication(malValuePtr obj, malEnvPtr env)
	300	{
	301	if (const malSequence* seq = isPair(obj)) {
	302	if (malSymbol* sym = DYNAMIC_CAST(malSymbol, seq->first())) {
	303	if (malEnvPtr symEnv = env->find(sym->value())) {
	304	malValuePtr value = sym->eval(symEnv);
	305	if (malLambda* lambda = DYNAMIC_CAST(malLambda, value)) {
	306	return lambda->isMacro() ? lambda : NULL;
	307	}
	308	}
	309	}
	310	}
	311	return NULL;
	312	}
	313
	314	static malValuePtr macroExpand(malValuePtr obj, malEnvPtr env)
315	{
316	while (const malLambda* macro = isMacroApplication(obj, env)) {
317	const malSequence* seq = STATIC_CAST(malSequence, obj);
494c1608	318	obj = macro->apply(seq->begin() + 1, seq->end());
2f61492a ST	319	}
	320	return obj;
	321	}
	322
	323	static const char* macroTable[] = {
	324	"(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))",
	325	"(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))",
	326	};
	327
	328	static void installMacros(malEnvPtr env)
	329	{
f01c2683 ST	330	for (auto &macro : macroTable) {
f01c2683 ST	331	rep(macro, env);
2f61492a ST	332	}
	333	}
	334
	335	static const char* malFunctionTable[] = {
	336	"(def! list (fn* (& items) items))",
	337	"(def! not (fn* (cond) (if cond false true)))",
	338	"(def! >= (fn* (a b) (<= b a)))",
	339	"(def! < (fn* (a b) (not (<= b a))))",
	340	"(def! > (fn* (a b) (not (<= a b))))",
	341	"(def! load-file (fn* (filename) \
	342	(eval (read-string (str \"(do \" (slurp filename) \")\")))))",
	343	"(def! map (fn* (f xs) (if (empty? xs) xs \
	344	(cons (f (first xs)) (map f (rest xs))))))",
	345	};
	346
	347	static void installFunctions(malEnvPtr env) {
f01c2683 ST	348	for (auto &function : malFunctionTable) {
f01c2683 ST	349	rep(function, env);
2f61492a ST	350	}
2f61492a ST	351	}
cb252845 ST	352
	353	// Added to keep the linker happy at step A
	354	malValuePtr readline(const String& prompt)
	355	{
	356	String input;
	357	if (s_readLine.get(prompt, input)) {
	358	return mal::string(input);
	359	}
	360	return mal::nilValue();
	361	}
	362