{"id":393456,"date":"2024-11-10T01:27:55","date_gmt":"2024-11-10T01:27:55","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/understanding-causality-errors-when-using-pre-and-last-in-a-scade-program\/"},"modified":"2024-11-12T10:42:33","modified_gmt":"2024-11-12T10:42:33","slug":"understanding-causality-errors-when-using-pre-and-last-in-a-scade-program","status":"answered","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/understanding-causality-errors-when-using-pre-and-last-in-a-scade-program\/","title":{"rendered":"Understanding causality errors when using `pre` and `last` in a Scade program."},"content":{"rendered":"

<div><div>In Scade language referece<\/code>, these is a code sample illustrate the causality error for variable y:<\/div><div><\/code><\/div><div>type T = enum {a, b, c};<\/div><div>node WhenBlkSample(x: T) returns (y: T last = b)<\/div><div>let<\/div><div>&nbsp; activate when y match<\/div><div>&nbsp; | a: y = a -> pre(y);<\/div><div>&nbsp; | b: y = x;<\/div><div>&nbsp; | c: -- empty<\/div><div>&nbsp; returns ..;<\/div><div>tel<\/div><div><\/code><\/code><\/div><br><div>The output of the scade compiler (kcg) is as the following<\/div><br><div><\/code><\/div><div>*** Causality Error (ERR_400): Causality error<\/div><div>&nbsp; at file ..., line 5, character 7<\/div><div>&nbsp; at path whenBlkSample\/_:a:y=<\/div><div>&nbsp;the definition of shared flow y depends on flow y via the control context ;<\/div><div>&nbsp; at file ..., line 2, character 34<\/div><div>&nbsp; at path whenBlkSample\/y\/<\/div><div>&nbsp;the definition of flow y depends on shared flow y via a control block ;<\/div><div><\/code><\/code><\/div><br><div>I still have trouble to understand it. Could anyone give some insight?<\/div><\/div><\/p>\n","protected":false},"template":"","class_list":["post-393456","topic","type-topic","status-answered","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\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