some small refactoring

ml_date.cpp

@@ -2,8 +2,8 @@
 #include "ml_date.h"
 
 long now() {	// get-universal-time
-	time_t t = std::time(0);
-	long int now = static_cast<long int>(t);
+	time_t t = std::time(nullptr);
+	auto now = static_cast<long int>(t);
 
 	return now;
 }
@@ -16,7 +16,7 @@ long get_gmt_localtime_offset() {
 	return offset;
 }
 
-std::string date_to_string(const long datetime, const std::string format) {
+std::string date_to_string(const long datetime, const std::string& format) {
 	// std::locale::global(std::locale("en-US.UTF8"));
 
 	time_t timestamp = datetime;
@@ -27,7 +27,7 @@ std::string date_to_string(const long datetime, const std::string format) {
 		return result;
 	}
 
-	throw std::runtime_error("date_to_string invalid date string or format");
+	throw std::runtime_error("date_to_string, invalid date string or format (" + std::to_string(datetime) + ", " + format + ")" );
 }
 
 time_t time_to_epoch ( const struct tm *ltm, int utcdiff ) {
@@ -37,12 +37,11 @@ time_t time_to_epoch ( const struct tm *ltm, int utcdiff ) {
 							 31+28+31+30+31+30+31+31+30+31, 31+28+31+30+31+30+31+31+30+31+30, 31+28+31+30+31+30+31+31+30+31+30+31};
 
 	long tyears, tdays, leaps, utc_hrs;
-   int i;
 
 	tyears = ltm->tm_year - 70 ; // tm->tm_year is from 1900.
 	leaps = (tyears + 2) / 4;
 	// no of next two lines until year 2100.
-   //i = (ltm->tm_year – 100) / 100;
+	//int i = (ltm->tm_year – 100) / 100;
 	//leaps -= ( (i/4)*3 + i%4 );
 
 	tdays = mon_days[ltm->tm_mon];
@@ -57,7 +56,7 @@ time_t time_to_epoch ( const struct tm *ltm, int utcdiff ) {
 long string_to_date(const std::string &datestr, const std::string &format) {
 	// format for example "%d.%m.%Y";
 
-	struct tm tm;
+	struct tm tm{};
 	memset(&tm, 0, sizeof(tm));
 	if (strptime(datestr.c_str(), format.c_str(), &tm)) {
 		time_t curTime;
@@ -76,11 +75,11 @@ long string_to_date(const std::string &datestr, const std::string &format) {
 		return time_to_epoch(timeinfo, 0);
 	}
 
-	throw std::runtime_error("invalid date string or format (" + datestr + ", " + format + ")" );
+	throw std::runtime_error("string_to_date, invalid date string or format (" + datestr + ", " + format + ")" );
 }
 
 
-long add_to_date(const long datetime, const long quantity, const std::string &part) {
+long add_to_date(const long datetime, const int quantity, const std::string &part) {
 	// part is one of 'year', 'month', 'day', 'hour', 'minute' or 'second'
 
 	// very basic implementation, just for now - no timezones DST etc
@@ -100,7 +99,7 @@ long add_to_date(const long datetime, const long quantity, const std::string &pa
 	} else if (part == "second") {
 		tm->tm_sec += quantity;
 	} else {
-		// TODO exception here
+		throw std::runtime_error("add_to_date, part to add (" + part + ")" );
 	}
 
 	return mktime(tm);	// mktime is quite slow!

ml_date.h

@@ -11,9 +11,9 @@ long now();
 
 long get_gmt_localtime_offset();
 
-std::string date_to_string(const long datetime, const std::string format);
+std::string date_to_string(const long datetime, const std::string &format);
 
 long string_to_date(const std::string &datestr, const std::string &format);
 
-long add_to_date(const long datetime, const long quantity, const std::string &part);
+long add_to_date(const long datetime, const int quantity, const std::string &part);
 

ml_io.cpp

@@ -55,19 +55,17 @@ bool is_path_file(const std::string &path) {
 }
 
 bool is_path_dir(const std::string &path) {
-	struct stat buf;
+	struct stat buf{};
 	stat(path.c_str(), &buf);
 	return (bool) S_ISDIR(buf.st_mode);
 }
 
 int mk_path_dir(const std::string &path) {
-	int r = ::mkdir(path.c_str(), 0755);
-	return r;
+	return ::mkdir(path.c_str(), 0755);
 }
 
 int rm_path_dir(const std::string &path) {
-	int r = ::rmdir(path.c_str());
-	return r;
+	return ::rmdir(path.c_str());
 }
 
 MlValue exec_system_cmd(const std::string &cmd) {

ml_string.cpp

@@ -81,7 +81,7 @@ std::vector<std::vector<std::string>> regexp_tokens(const std::string &str, cons
 				captured_subgroups.push_back(res[i]);
 			}
 		}
-		if (captured_subgroups.size() > 0)
+		if (!captured_subgroups.empty())
 			captured_groups.push_back(captured_subgroups);
 
 		searchStart += res.position() + res.length();
@@ -119,7 +119,7 @@ std::string string_trim(std::string s, const std::string &chars_to_trim, const s
 }
 
 std::string string_padd(const std::string &str, int pad_len, char fill_char, bool from_right) {
-	int str_len = str.length();
+	auto str_len = str.length();
 
 	if (str_len == pad_len)
 		return str;