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Add variability change for these functions. #3610

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Add variability change for these functions. #3610

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5878d52
Add variability change for these functions.
HansOlsson Nov 12, 2024
7b49a58
After some thinking I believe this is how we handle multiple outputs.
HansOlsson Nov 12, 2024
b760714
Update chapters/operatorsandexpressions.tex
HansOlsson Nov 20, 2024
3acf849
To handle the other case for GenerateEvents-functions.
HansOlsson Nov 22, 2024
b1cb03a
Update chapters/operatorsandexpressions.tex
HansOlsson Nov 25, 2024
aa0e9ec
Forgot variability for inputs previously.
HansOlsson Nov 29, 2024
fb13f66
State that variables in functions being discrete-time is a bit more c…
HansOlsson Nov 29, 2024
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6 changes: 5 additions & 1 deletion chapters/operatorsandexpressions.tex
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Expand Up @@ -1644,10 +1644,14 @@ \subsection{Discrete-Time Expressions}\label{discrete-time-expressions}
Note that \lstinline!rem! and \lstinline!mod! generate events but are not discrete-time expressions.
In other words, relations inside \lstinline!noEvent!, such as \lstinline!noEvent(x>1)!, are not discrete-time expressions.
\end{nonnormative}
\item
Unless inside \lstinline!noEvent!: Function calls where the function has annotation \lstinline!GenerateEvents = true! (\Cref{modelica:GenerateEvents}) and the output does not contain a subtype of \lstinline!Real!.
For a function call returning multiple return values (see \cref{output-formal-parameters-of-functions}) the variability is decided separately for each output.
These calls will generate events, \Cref{modelica:GenerateEvents}.
\item
The functions \lstinline!pre!, \lstinline!edge!, and \lstinline!change! result in discrete-time expressions.
\item
Expressions in functions behave as though they were discrete-time expressions.
Expressions in functions not having annotation \lstinline!GenerateEvents = true! (\Cref{modelica:GenerateEvents}), behave as though they were discrete-time expressions.
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Don't we need more specification of variability inside functions that do have GenerateEvents = true? We don't want all expressions inside such function bodies to get non-discrete-time variability, right?

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@henrikt-ma henrikt-ma Nov 29, 2024 •
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This could be a start…

Suggested change
Expressions in functions not having annotation \lstinline!GenerateEvents = true! (\Cref{modelica:GenerateEvents}), behave as though they were discrete-time expressions.
The variability of expressions inside functions depends upon the \lstinline!GenerateEvents! annotation (\Cref{modelica:GenerateEvents}).
With \lstinline!GenerateEvents = true!, expression variability is determined according to the same rules as outside of functions.
Otherwise, all expressions have at most discrete-time variability (some expressions, such as function inputs and literals have lower variability).

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That was the intent of the text I wrote (ignoring the misplaced trailing quotes).

The overall structure of that secition is that it specifies when expressions have lower variability. Stating that functions having GenerateEvents=true use the same rule as non-function is thus not needed, and similarly there is no need to say "at most discrete-time" as the less variable cases should already be handled.

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OK, makes sense. The formulation is a bit unusual, though, shouldn't we simply say:

Suggested change
Expressions in functions not having annotation \lstinline!GenerateEvents = true! (\Cref{modelica:GenerateEvents}), behave as though they were discrete-time expressions.
Expressions in functions not having annotation \lstinline!GenerateEvents = true! (\Cref{modelica:GenerateEvents}).

This item would then look better before or after Expressions in a clocked discrete-time partition.

I also think there is a missing \cref{discrete-time-expressions} link to this section from this item in functions.tex, and the item would need to be updated according to whatever semantics we come up with here:

Components of a function will inside the function behave as though they had discrete-time variability.

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The "behave as though they were discrete-time expressions." have been present for quite some time on some of the entries. I don't want to change them as part of this PR.

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And added the other reference.

\end{itemize}

Inside an \lstinline!if!-expression, \lstinline!if!-clause, \lstinline!while!-statement or \lstinline!for!-clause, that is controlled by a non-discrete-time (that is continuous-time, but not discrete-time) switching expression and not in the body of a \lstinline!when!-clause, it is not legal to have assignments to discrete-time variables, equations between discrete-time expressions, or real elementary relations/functions that should generate events.
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