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())
);
}
}
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);
}
}
}
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());
}
}
}