{"id":1411,"date":"2012-11-23T13:25:44","date_gmt":"2012-11-23T11:25:44","guid":{"rendered":"http:\/\/mariusbancila.ro\/blog\/?p=1411"},"modified":"2012-11-23T13:25:44","modified_gmt":"2012-11-23T11:25:44","slug":"cpplinq-set-operators","status":"publish","type":"post","link":"https:\/\/mariusbancila.ro\/blog\/2012\/11\/23\/cpplinq-set-operators\/","title":{"rendered":"cpplinq: set operators"},"content":{"rendered":"

In the previous posts<\/a> I introduced cpplinq<\/a>, a C++ template library that provides .NET-like query operators for sequences of objects in C++11. In this third installment I will discuss the set operators the library provides.<\/p>\n

There are four set operators: distinct<\/strong>, union_with<\/strong> (called so because union is a keyword in C++), intersect_with<\/strong> (suffix _with is for consistency with the union operator) and except<\/strong>. These operators should be pretty straight forward: distinct<\/strong> eliminates the duplicate elements from a sequence, yielding a new sequence with only the distinct elements (in the order their original order), union_with<\/strong> produces the set union of two sequences, intersect_with<\/strong> produces the set intersection of two sequences and except<\/strong> produces the set difference of two sequences. <\/p>\n

Before seeing some examples, it worth nothing that all these operators delay the traversal of the sequences until the resulting object is enumerated.<\/p>\n

Let’s see some examples:<\/p>\n

\r\nint numbers[] = {5,4,3,2,1,2,3,4,5};\r\nauto result = from_array(numbers) >> distinct() >> to_vector(); \/\/ yields {5,4,3,2,1}\r\n<\/pre>\n
\r\nauto result = empty<int>() >> union_with(range(1,5)) >> to_vector(); \/\/ yields {1,2,3,4,5}\r\n\r\nint set1[] = {5,4,3,2,1,2,3,4,5};\r\nint set2[] = {4,5,6,7};\r\nauto set3 = from_array(set1) >> union_with(from_array(set2)) >> to_vector(); \/\/ yields {5,4,3,2,1,6,7}\r\nauto set4 = from_array(set2) >> union_with(from_array(set1)) >> to_vector(); \/\/ yields {4,5,6,7,3,2,1}\r\n<\/pre>\n
\r\nauto result1 = empty<int>() >> intersect_with( range(0, 10) ) >> to_vector(); \/\/ yields {}\r\nauto result2 = range(0, 10) >> intersect_with( empty<int>() ) >> to_vector(); \/\/ yields {}\r\n\r\nint set1[] = {5,4,3,2,1,2,3,4,5};\r\nint set2[] = {4,5,6};\r\nauto set3 = from_array(set1) >> intersect_with(from_array(set2)) >> to_vector(); \/\/ yields {5,4}\r\nauto set3 = from_array(set2) >> intersect_with(from_array(set1)) >> to_vector(); \/\/ yields {4,5}\r\n<\/pre>\n
\r\nauto result1 = empty<int>() >> except( range(0, 10) ) >> to_vector(); \/\/ yields {}\r\nauto result2 = range(0, 10) >> except( empty<int>() ) >> to_vector(); \/\/ yields {0,1,2,3,4,5,6,7,8,9}\r\n\r\nint set1[] = {5,4,3,2,1,2,3,4,5};\r\nint set2[] = {4,5,6,7};\r\nauto set3 = from_array(set1) >> except(from_array(set2)) >> to_vector(); \/\/ yields {3,2,1}\r\nauto set4 = from_array(set2) >> except(from_array(set1)) >> to_vector(); \/\/ yields {6,7}\r\n<\/pre>\n
You can learn more about these operators (and the others that are implemented) by reading the cpplinq query operators documentation<\/a>.<\/p>\n
CodeProject<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
In the previous posts I introduced cpplinq, a C++ template library that provides .NET-like query operators for sequences of objects in C++11. In this third installment I will discuss the set operators the library provides. There are four set operators: distinct, union_with (called so because union is a keyword in C++), intersect_with (suffix _with is … 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":false,"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":[451,327,138,328,334,253],"class_list":["post-1411","post","type-post","status-publish","format-standard","hentry","category-c","tag-c","tag-cpplinq","tag-library","tag-linq-2","tag-operators","tag-query"],"aioseo_notices":[],"aioseo_head":"\n\t\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\n\t\t