added catch handler for syntax error when processing file args, for a clear error message with line number included

main.cpp

@@ -77,6 +77,10 @@ int main(int argc, const char * argv[]) {
                 done = false;
                 std::ifstream file {argv[i]};
                 proc.eval(file, done);
+            } catch (const syntax_error& err) {
+                std::cerr << "curly: syntax error in " << argv[i];
+                std::cerr << ", at line " << err.lineno();
+                std::cerr << ": " << err.what() << '\n';
             } catch (const std::runtime_error& ex) {
                 std::cerr << "curly: " << ex.what() << '\n';
             }