1 files changed, 333 insertions, 0 deletions
diff --git a/src/eval.c b/src/eval.c
new file mode 100644
index 0000000..c1a6a10
--- /dev/null
+++ b/src/eval.c
@@ -0,0 +1,333 @@
+#include "eval.h"
+#include "ast.h"
+#include "object.h"
+#include "token.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+
+static struct object obj_null = {
+	OBJECT_NULL,
+	2,
+	{ 0 },
+};
+static struct object obj_true = {
+	OBJECT_BOOL,
+	2,
+	.boolean = true,
+};
+static struct object obj_false = {
+	OBJECT_BOOL,
+	2,
+	.boolean = false,
+};
+
+static inline struct object *
+get_bool_object(bool val)
+{
+	struct object *obj = val ? &obj_true : &obj_false;
+	return obj;
+}
+
+static struct object *
+new_error(char *fmt, ...)
+{
+	char *msg = malloc(1024);
+	struct object *obj = object_new(msg);
+
+	va_list args;
+	va_start(args, fmt);
+	vsprintf(obj->error.msg, fmt, args);
+	va_end(args);
+
+	return obj;
+}
+
+static struct object *
+eval_statements(struct environment *env, struct vector *sts)
+{
+	size_t i;
+	struct object *res;
+	struct statement *st;
+	vector_foreach(sts, i, st) {
+		res = eval(env, st);
+		if (res->type == OBJECT_RETURN || res->type == OBJECT_ERROR) {
+			return res;
+		}
+	}
+	return res;
+}
+
+static inline struct object *
+eval_bang_prefix_expression(struct environment *env, struct object *right)
+{
+	struct object *res;
+	res = get_bool_object(!right->integer);
+	object_unref(right);
+	return res;
+}
+
+static inline struct object *
+eval_minus_prefix_expression(struct environment *env, struct object *right)
+{
+	struct object *res;
+	if (right->type != OBJECT_INT) {
+		struct object *error = new_error("unknown operator: -%s",
+				object_type_print(right->type));
+		object_unref(right);
+		return error;
+	}
+	res = object_new(-right->integer);
+	object_unref(right);
+	return res;
+}
+
+static struct object *
+eval_prefix_expression(struct environment *env, struct token op,
+		struct object *right)
+{
+	struct object *res;
+	switch (op.type) {
+	case TOKEN_BANG:
+		return eval_bang_prefix_expression(env, right);
+	case TOKEN_MINUS:
+		return eval_minus_prefix_expression(env, right);
+	default:;
+		char buf[256];
+		struct object *error = new_error("unknown operator: %s%s",
+				slice_sprint(&op.literal, buf), object_type_print(right->type));
+		object_unref(right);
+		return error;
+	}
+}
+
+static inline struct object *
+eval_integer_infix_expression(struct environment *env, struct token op,
+		struct object *left, struct object *right)
+{
+	bool bres;
+	struct object *ires;
+	switch (op.type) {
+	case TOKEN_PLUS:
+		ires = object_new(left->integer + right->integer);
+		break;
+	case TOKEN_MINUS:
+		ires = object_new(left->integer - right->integer);
+		break;
+	case TOKEN_ASTERISK:
+		ires = object_new(left->integer * right->integer);
+		break;
+	case TOKEN_SLASH:
+		ires = object_new(left->integer / right->integer);
+		break;
+	case TOKEN_LT:
+		bres = left->integer < right->integer;
+		goto boolres;
+	case TOKEN_GT:
+		bres = left->integer > right->integer;
+		goto boolres;
+	case TOKEN_EQ:
+		bres = left->integer == right->integer;
+		goto boolres;
+	case TOKEN_NOTEQ:
+		bres = left->integer != right->integer;
+		goto boolres;
+	default:;
+		char buf[256];
+		struct object *error = new_error("unknown operator: %s %s %s",
+				object_type_print(left->type), slice_sprint(&op.literal, buf),
+				object_type_print(right->type));
+		object_unref(left);
+		object_unref(right);
+		return error;
+	}
+	object_unref(left);
+	object_unref(right);
+	return ires;
+boolres:
+	object_unref(left);
+	object_unref(right);
+	return get_bool_object(bres);
+}
+
+static inline struct object *
+eval_infix_expression(struct environment *env, struct token op,
+		struct object *left, struct object *right)
+{
+	if (left->type == OBJECT_INT && right->type == OBJECT_INT) {
+		return eval_integer_infix_expression(env, op, left, right);
+	}
+	bool res;
+	switch (op.type) {
+	case TOKEN_EQ:
+		res = left->integer == right->integer;
+		break;
+	case TOKEN_NOTEQ:
+		res = left->integer != right->integer;
+		break;
+	default:;
+		char buf[256];
+		struct object *error;
+		if (left->type != right->type) {
+			error = new_error("type mismatch: %s %s %s",
+					object_type_print(left->type), slice_sprint(&op.literal, buf),
+					object_type_print(right->type));
+		} else {
+			error = new_error("unknown operator: %s %s %s",
+					object_type_print(left->type), slice_sprint(&op.literal, buf),
+					object_type_print(right->type));
+		}
+		object_unref(left);
+		object_unref(right);
+		return error;
+	}
+	object_unref(left);
+	object_unref(right);
+	return get_bool_object(res);
+}
+
+static inline struct object *
+eval_if_expression(struct environment *env, struct if_expression *expr)
+{
+	struct object *cond = eval(env, expr->condition);
+	struct object *res;
+	if (cond->boolean) {
+		res = eval(env, expr->consequence);
+	} else if (expr->alternative) {
+		res = eval(env, expr->alternative);
+	} else {
+		res = &obj_null;
+	}
+	object_unref(cond);
+	return res;
+}
+
+static inline struct object *
+eval_call_expression(struct environment *env, struct expression *expr)
+{
+	struct object *func = eval(env, expr->call.func);
+	if (func->type == OBJECT_ERROR) {
+		return func;
+	} else if (func->type != OBJECT_FUNC) {
+		char buf[256];
+		struct object *err = new_error("not a function: %s",
+				object_sprint(func, buf));
+		object_unref(func);
+		return err;
+	}
+	size_t i;
+	struct expression *arg;
+	struct environment *fenv = environment_new_enclosed(env);
+	vector_foreach(expr->call.arguments, i, arg) {
+		struct object *obj = eval(env, arg);
+		if (obj->type == OBJECT_ERROR) {
+			object_unref(func);
+			return obj;
+		}
+		struct expression *param = func->func.params->values[i];
+		environment_set(fenv, param->ident.value, obj);
+		object_unref(obj);
+	}
+	struct object *res = eval(fenv, func->func.body);
+	if (res->type == OBJECT_RETURN) {
+		struct object *ret = res;
+		res = ret->retrn.value;
+		object_ref(res);
+		object_unref(ret);
+	}
+	object_unref(func);
+	environment_destroy(fenv);
+	return res;
+}
+
+struct object *
+eval_expression(struct environment *env, struct expression *expr)
+{
+	struct object *res = NULL;
+	switch (expr->type) {
+	case EXPRESSION_INT:
+		res = object_new(expr->integer.value);
+		return res;
+	case EXPRESSION_BOOL:
+		return expr->boolean.value ? &obj_true : &obj_false;
+	case EXPRESSION_PREFIX:
+		res = eval(env, expr->prefix.right);
+		if (res == OBJECT_ERROR) return res;
+		return eval_prefix_expression(env, expr->token, res);
+	case EXPRESSION_INFIX:;
+		struct object *left = eval(env, expr->infix.left);
+		if (left == OBJECT_ERROR) return res;
+		struct object *right = eval(env, expr->infix.right);
+		if (right == OBJECT_ERROR) {
+			object_unref(left);
+			return right;
+		}
+		return eval_infix_expression(env, expr->token, left, right);
+	case EXPRESSION_IF:
+		return eval_if_expression(env, &expr->cond);
+	case EXPRESSION_IDENT:
+		res = environment_get(env, &expr->ident.value);
+		if (!res) {
+			char ibuf[256];
+			return new_error("not declared: %s",
+					slice_sprint(&expr->ident.value, ibuf));
+		}
+		object_ref(res);
+		return res;
+	case EXPRESSION_FUNC:
+		res = object_new(expr);
+		return res;
+	case EXPRESSION_CALL:
+		return eval_call_expression(env, expr);
+	default:
+		return NULL;
+	}
+}
+
+struct object *
+eval_statement(struct environment *env, struct statement *st)
+{
+	struct object *val;
+	switch (st->type) {
+	case STATEMENT_EXPRESSION:
+		return eval(env, st->expr.expr);
+	case STATEMENT_BLOCK:
+		return eval_statements(env, st->block.statements);
+	case STATEMENT_RETURN:
+		val = eval(env, st->retrn.value);
+		if (val->type == OBJECT_ERROR) return val;
+		struct object *res = object_new(val);
+		return res;
+	case STATEMENT_LET:
+		val = eval(env, st->let.value);
+		if (val->type == OBJECT_ERROR) return val;
+		struct object *old = environment_set(env, st->let.name->value, val);
+		if (old) object_unref(old);
+		object_unref(val);
+	default:
+		return NULL;
+	}
+}
+
+struct object *
+eval_program(struct environment *env, struct program *prog)
+{
+	size_t i;
+	struct object *res = NULL;
+	struct statement *st;
+	vector_foreach(prog->statements, i, st) {
+		if (res) object_unref(res);
+		res = eval(env, st);
+		if (res) {
+			if (res->type == OBJECT_RETURN) {
+				struct object *val = res->retrn.value;
+				object_ref(val);
+				object_unref(res);
+				return val;
+			} else if (res->type == OBJECT_ERROR) {
+				return res;
+			}
+		}
+	}
+	return res;
+}