Initialization of variables in C++ can have several forms:<\/p>\n
C++11 introduced a generalized syntax for initialization with a braced initializer list, referred to as braced-init-list. Initialization with braced-init-list is called list initialization. There are two types of list initialization, each having multiple forms (check the above links), but simplified, we can have:<\/p>\n
Prior to C++17 the type for all the following objects (a<\/tt>, b<\/tt>, c<\/tt> and d<\/tt>) is deduced to std::initializer_list<int><\/tt>. There is no difference between the direct-list-initialization and the copy-list-initialization on the result of the type deduction.<\/p>\n This, however, changed in C++17 that introduced the following rules:<\/p>\n As a result, the example above changes so that a<\/tt> and c<\/tt> are still std::initializer_list<int><\/tt> but b<\/tt> is deduced as an int<\/tt> and d<\/tt> is ill-formed, because there is more than one value in the brace-init-list.<\/p>\n For more information about these changes see N3922: New Rules for auto deduction from braced-init-list<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":" Initialization of variables in C++ can have several forms: default initialization: std::string s; value initialization: std::string s{}; direct initialization: std::string s(“demo”); copy initialization: std::string s = “demo”; list initialization: std::string s{‘d’, ‘e’, ‘m’, ‘o’}; aggregate initialization: char s[5] = {‘d’, ‘e’, ‘m’, ‘o’}; reference initialization: char& c = s[0]; C++11 introduced a generalized syntax for … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_uag_custom_page_level_css":"","advgb_blocks_editor_width":"","advgb_blocks_columns_visual_guide":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[7],"tags":[75,451,475,512],"class_list":["post-2433","post","type-post","status-publish","format-standard","hentry","category-c","tag-auto","tag-c","tag-c17","tag-initialization"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\r\nauto a = {42}; \/\/ std::initializer_list<int>\r\nauto b {42}; \/\/ std::initializer_list<int>\r\nauto c = {1, 2}; \/\/ std::initializer_list<int>\r\nauto d {1, 2}; \/\/ std::initializer_list<int>\r\n<\/pre>\n\n
\r\nauto a = {42}; \/\/ std::initializer_list<int>\r\nauto b {42}; \/\/ int\r\nauto c = {1, 2}; \/\/ std::initializer_list<int>\r\nauto d {1, 2}; \/\/ error, too many \r\n<\/pre>\n