From 3d54ed9fb3a7e3b4e11db0894321ba7757e106fc Mon Sep 17 00:00:00 2001
From: Vaclav Tvrdik <tvrdik@i3.cz>
Date: Sun, 7 Mar 2021 18:40:26 +0100
Subject: [PATCH] better handling of comments

---
 Readme.md |  2 +-
 ml.cpp    | 30 ++++++++++++++++++------------
 ml.h      |  4 ++--
 ml_io.cpp |  2 +-
 4 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/Readme.md b/Readme.md
index e6357ea..9fcf0e2 100644
--- a/Readme.md
+++ b/Readme.md
@@ -1,6 +1,5 @@
 
 ### BUGS
-- see malformed_program - wrong parsing of comments - probably comment with "
 
 ### TODO
 - test whether AIG,,,10 csv row is parsed
@@ -40,6 +39,7 @@
 - format (printf)
 - setq
 - mapcar (funcall, apply)
+- delete UNIT (replace it by nil)
 
 #### Performance
 - push_back - repeatedly without reserving size
diff --git a/ml.cpp b/ml.cpp
index fe9ba00..7216b9c 100644
--- a/ml.cpp
+++ b/ml.cpp
@@ -736,8 +736,22 @@ MlValue MlValue::eval(MlEnvironment &env) {
 	}
 }
 
-void skip_whitespace(const std::string &s, int &ptr) {
-	while (isspace(s[ptr])) { ptr++; }
+void skip_whitespace(std::string &s, int &ptr);
+
+void erase_comments(std::string &s, int &ptr) {
+    while (s[ptr] == ';') {
+        int save_ptr = ptr;
+        while (s[save_ptr] != '\n' && save_ptr < int(s.length())) { save_ptr++; }
+        s.erase(ptr, save_ptr - ptr);
+
+        skip_whitespace(s, ptr);
+    }
+}
+
+void skip_whitespace(std::string &s, int &ptr) {
+    while (isspace(s[ptr])) { ptr++; }
+
+	erase_comments(s, ptr);
 }
 
 // Parse a single value and increment the pointer
@@ -745,16 +759,8 @@ void skip_whitespace(const std::string &s, int &ptr) {
 MlValue parse(std::string &s, int &ptr) {
 	skip_whitespace(s, ptr);
 
-	while (s[ptr] == ';') {
-		// If this is a comment
-		int save_ptr = ptr;
-		while (s[save_ptr] != '\n' && save_ptr < int(s.length())) { save_ptr++; }
-		s.erase(ptr, save_ptr - ptr);
-		skip_whitespace(s, ptr);
-
-		if (s.substr(ptr, s.length() - ptr - 1) == "")
-			return MlValue();
-	}
+	if (s[ptr] == ';')
+		throw std::runtime_error("this should never happen!");
 
 
 	if (s == "") {
diff --git a/ml.h b/ml.h
index 9152f37..39b1973 100644
--- a/ml.h
+++ b/ml.h
@@ -16,7 +16,7 @@ class MlValue;
 class MlEnvironment {
 public:
     // Default constructor
-    MlEnvironment() : parent_scope(NULL) {}
+    MlEnvironment() : parent_scope(nullptr) {}
 
     // Does this environment, or its parent environment,
     // have this atom in scope?
@@ -120,7 +120,7 @@ public:
 
     bool is_number() const;
 
-    // Get the "truthy" boolean value of this value.
+    // Get the boolean value of this value.
     bool as_bool() const;
 
     // Get this item's integer value
diff --git a/ml_io.cpp b/ml_io.cpp
index 6abc509..4bb161f 100644
--- a/ml_io.cpp
+++ b/ml_io.cpp
@@ -10,7 +10,7 @@ std::string read_file_contents(const std::string &filename) {
 	std::ifstream f;
 	f.open(filename.c_str());
 	if (!f)
-		throw std::runtime_error("could not open file");
+		throw std::runtime_error("could not open file (" + filename + ")");
 
 	f.seekg(0, std::ios::end);
 	std::string contents;