Beispiel #1
0
malValuePtr EVAL(malValuePtr ast, malEnvPtr env)
{
    while (1) {
        const malList* 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 == "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 == "quasiquote") {
                checkArgsIs("quasiquote", 1, argCount);
                ast = quasiquote(list->item(1));
                continue; // TCO
            }

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

        // 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(), env);
        }
    }
}
Beispiel #2
0
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());
        }
    }
}