From a529b6e3f6662e06a580541d2b21f57770cdb30f Mon Sep 17 00:00:00 2001
From: Eatswap <root@eatswap.org>
Date: Sun, 11 Dec 2022 20:20:49 +0800
Subject: [PATCH] fix: specify start, allow parse file as cmd arg

---
 DragonLisp.y         | 2 ++
 DragonLispDriver.cpp | 4 +++-
 main.cpp             | 6 ++++--
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/DragonLisp.y b/DragonLisp.y
index 2a5f8e0..e937c93 100644
--- a/DragonLisp.y
+++ b/DragonLisp.y
@@ -96,6 +96,8 @@ namespace DragonLisp {
 
 %define parse.error verbose
 
+%start S
+
 %%
 
 S
diff --git a/DragonLispDriver.cpp b/DragonLispDriver.cpp
index aba1dc1..6fc9488 100644
--- a/DragonLispDriver.cpp
+++ b/DragonLispDriver.cpp
@@ -14,8 +14,10 @@ DLDriver::~DLDriver() {
 
 int DLDriver::parse(const std::string& f) {
 	std::ifstream in(f);
-	if (!in.good())
+	if (!in.good()) {
+		std::printf("Could not open file %s\n", f.c_str());
 		return 1;
+	}
 	return this->parse(in, f);
 }
 
diff --git a/main.cpp b/main.cpp
index 48997e1..42a62b9 100644
--- a/main.cpp
+++ b/main.cpp
@@ -2,7 +2,9 @@
 
 #include "DragonLispDriver.hh"
 
-int main() {
+int main(int argc, char** argv) {
 	DragonLisp::DLDriver driver;
-	return driver.parse(std::cin);
+	if (argc <= 1)
+		return driver.parse(std::cin);
+	return driver.parse(argv[1]);
 }