Env+Eval: Tweak (and) and (-)

src/env/functions/operators.cpp

@@ -30,7 +30,8 @@ void Environment::loadOperators()
 	ADD_FUNCTION(
 		"-",
 		{
-			if (SIZE() == 0) {
+			size_t length = SIZE();
+			if (length == 0) {
 				return makePtr<Number>(0);
 			}
 
@@ -38,6 +39,10 @@ void Environment::loadOperators()
 			VALUE_CAST(number, Number, (*begin));
 			int64_t result = number->number();
 
+			if (length == 1) {
+				return makePtr<Number>(-result);
+			}
+
 			// Skip the first node
 			for (auto it = begin + 1; it != end; ++it) {
 				VALUE_CAST(number, Number, (*it));

src/eval-special-form.cpp

@@ -184,7 +184,7 @@ ValuePtr Eval::evalTry(const ValueVector& nodes, EnvironmentPtr env)
 // (and 1 2 3)
 void Eval::evalAnd(const ValueVector& nodes, EnvironmentPtr env)
 {
-	ValuePtr result;
+	ValuePtr result = makePtr<Constant>(Constant::True);
 	for (auto node : nodes) {
 		m_ast = node;
 		m_env = env;