Changes between Version 12 and Version 13 of WritingEfficientMetaModelica

Timestamp:

2014-11-03T11:07:24+01:00 (10 years ago)

Author:

sjoelund.se

Comment:

--

WritingEfficientMetaModelica

@@ -88 +88 @@
 Try/else is implemented as syntactic sugar. It is executed as if it was the above matchcontinue statement, but is shorter to write.
 
+== Assign to metarecord fields directly ==
+
+MetaModelica uniontype records are a bit different than Modelica records: they are immutable, so you can't just assign to them. Especially since uniontypes may have several records.
+It is possible to list all fields and create a new record.
+But it is also possible to match a uniontype to become a metarecord (sadly not in assignments yet, though).
+Using this, it is possible to use dot-notation to access a field (member) of the record, and also to assign to it (given that it is not a function input).
+
+The following pattern seems to work well, and produces code that is easy to maintain (adding a field to PROGRAM will not require you to update this code).
+Assigning to two different fields will cause two allocations of the record though, so there is a cost of using this (for assigning to a single field, there is an optimized implementation that is faster than retrieving all the fields and calling the record constructor).
+
+{{{#!mo
+function removeInnerDiffFiledClasses
+  input Absyn.Program inProgram;
+  output Absyn.Program p := inProgram;
+algorithm
+  p := match p
+    case Absyn.PROGRAM()
+      equation
+        p.classes = List.map(p.classes, removeInnerDiffFiledClass);
+      then p;
+  end match;
+end removeInnerDiffFiledClasses;
+}}}
+
 == Avoid matchcontinue, use tail recursion ==
 `matchcontinue` is slow. Whenever possible, use `match` instead. This avoids calling `setjmp`.