{"metadata":{"image":[],"title":"","description":""},"api":{"url":"","auth":"required","params":[],"results":{"codes":[]},"settings":""},"next":{"description":"","pages":[]},"title":"Functional Operations","type":"basic","slug":"functional-combinators","excerpt":"How you can transform, combine and operate with sets in a functional way.","body":"We explore the functional operations provided by Lasp.  Each of these functions takes, as input, a single source collection and creates a single output collection.  The output will be maintained as the input is modified, and these operators can be chained arbitrarily.  \n[block:api-header]\n{\n  \"title\": \"Map Operation\"\n}\n[/block]\nFirst, declare a source set.\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> {ok, {SourceId, _, _, _}} = lasp:declare({<<\\\"source\\\">>, state_orset}, state_orset).\\n{ok,{{<<\\\"source\\\">>,state_orset},\\n     state_orset,\\n     [{clock,[{<<170,227,142,126,63,64,19,227,195,66,39,125,58,\\n                 195,75,134,148,109,168,...>>,\\n               1}]}],\\n     {state_orset,[]}}}\",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\nThen, declare a destination set.\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> {ok, {DestinationId, _, _, _}} = lasp:declare({<<\\\"destination\\\">>, state_orset}, state_orset).\\n{ok,{{<<\\\"destination\\\">>,state_orset},\\n     state_orset,\\n     [{clock,[{<<170,227,142,126,63,64,19,227,195,66,39,125,58,\\n                 195,75,134,148,109,168,...>>,\\n               1}]}],\\n     {state_orset,[]}}}\",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\nLet's map the values from one set into the other, and double the elements.\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> lasp:map(SourceId, fun(X) -> X * 2 end, DestinationId).\\nok\",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\nNow, we can add an element to the first set and see the results of the transformation in the destination set!\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> lasp:update(SourceId, {add, 1}, self()).               \\n{ok,{{<<\\\"source\\\">>,state_orset},\\n     state_orset,\\n     [{clock,[{<<170,227,142,126,63,64,19,227,195,66,39,125,58,\\n                 195,75,134,148,109,168,...>>,\\n               2}]}],\\n     {state_orset,[{1,\\n                    [{<<124,101,224,70,103,26,222,240,141,97,96,128,120,143,\\n                        228,148,...>>,\\n                      true}]}]}}}\\n> lasp:query(DestinationId).\\n{ok,{set,1,16,16,8,80,48,\\n         {[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]},\\n         {{[],[],[],[],[],[],[2],[],[],[],[],[],[],[],[],[]}}}}\\n> {ok, Result} = lasp:query(DestinationId), sets:to_list(Result).\\n[2]\",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\n\n[block:api-header]\n{\n  \"title\": \"Filter Operation\"\n}\n[/block]\nNow, assuming we still have the source set declared from the section above, we can apply a filter directly to it.\n\nFirst, let's declare somewhere to store the results.\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> {ok, {FilteredId, _, _, _}} = lasp:declare({<<\\\"filtered\\\">>, state_orset}, state_orset).      \\n{ok,{{<<\\\"filtered\\\">>,state_orset},\\n     state_orset,\\n     [{clock,[{<<170,227,142,126,63,64,19,227,195,66,39,125,58,\\n                 195,75,134,148,109,168,...>>,\\n               1}]}],\\n     {state_orset,[]}}}\",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\nNow, let's apply a filter that only allows even elements through.\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> lasp:filter(SourceId, fun(X) -> X rem 2 == 0 end, FilteredId). \\nok\",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\nSince the source set only has `1` in it, the filtered set should be empty!\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> {ok, Result1} = lasp:query(FilteredId), sets:to_list(Result1).\\n[]\",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\nBut, if we add an element to the set that's even, we should see the output in the filtered set.\n[block:code]\n{\n  \"codes\": [\n    {\n      \"code\": \"> lasp:update(SourceId, {add, 2}, self()).                                    {ok,{{<<\\\"source\\\">>,state_orset},\\n     state_orset,\\n     [{clock,[{<<170,227,142,126,63,64,19,227,195,66,39,125,58,\\n                 195,75,134,148,109,168,...>>,\\n               3}]}],\\n     {state_orset,[{1,\\n                    [{<<124,101,224,70,103,26,222,240,141,97,96,128,120,143,\\n                        228,148,...>>,\\n                      true}]},\\n                   {2,\\n                    [{<<82,188,56,236,83,244,32,79,114,44,4,33,148,226,184,...>>,\\n                      true}]}]}}}\\n                                                                                  \\n> {ok, Result2} = lasp:query(FilteredId), sets:to_list(Result2).\\n[2]                                                                                \",\n      \"language\": \"erlang\"\n    }\n  ]\n}\n[/block]\n\n[block:callout]\n{\n  \"type\": \"warning\",\n  \"title\": \"Fold Operation\",\n  \"body\": \"We avoid discussion of the fold operation here, as it's currently being revised and the interface i the prototype is less than desirable at the current moment.\"\n}\n[/block]","updates":[],"order":6,"isReference":false,"hidden":false,"sync_unique":"","link_url":"","link_external":false,"_id":"58f5cac2616bbb1b00d54abc","project":"5612c2a00fbdb60d00e4c7d1","createdAt":"2017-04-18T08:13:54.542Z","githubsync":"","user":"5612c290c0731b0d00625078","version":{"version":"0.0.1","version_clean":"0.0.1","codename":"","is_stable":true,"is_beta":true,"is_hidden":false,"is_deprecated":false,"categories":["5612c2a10fbdb60d00e4c7d5","58e6b64bc397de1b00173c09","58e6b68eb1eece19008b81fe","58e6b6d185ec873100be9734","58f5e5c2616bbb1b00d54c15","58f5eaa74c413f19007a2858","58f767a79c723f19004e1ca9"],"_id":"5612c2a00fbdb60d00e4c7d4","createdAt":"2015-10-05T18:34:08.611Z","releaseDate":"2015-10-05T18:34:08.611Z","__v":7,"project":"5612c2a00fbdb60d00e4c7d1"},"__v":0,"parentDoc":null,"category":{"sync":{"isSync":false,"url":""},"pages":[],"title":"Lasp","slug":"api","order":1,"from_sync":false,"reference":false,"_id":"58e6b68eb1eece19008b81fe","project":"5612c2a00fbdb60d00e4c7d1","version":"5612c2a00fbdb60d00e4c7d4","__v":0,"createdAt":"2017-04-06T21:43:42.570Z"}}