Clarify elsewhen initial #2647
Clarify elsewhen initial #2647
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chapters/equations.tex
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| @@ -748,7 +748,7 @@ \section{Initialization, initial equation, and initial algorithm}\label{initiali | |||
| (such as simulation or linearization). | |||
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| The equations of a when-clause are active during initialization, if and only if they are explicitly enabled with \lstinline!initial()!, and only in one of the two forms | |||
| \lstinline!when initial() then! or \lstinline!when {$\ldots$, initial(), $\ldots$} then! (and similarly for algorithms see below). In this case, the when-clause equations remain active during the | |||
| \lstinline!when initial() then! or \lstinline!when {$\ldots$, initial(), $\ldots$} then! (and similarly for \lstinline!elsewhen! and algorithms see below). In this case, the when-clause equations remain active during the | |||
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Perhaps when-statements would be more to the point, and the see below probably only refers to these?
| \lstinline!when initial() then! or \lstinline!when {$\ldots$, initial(), $\ldots$} then! (and similarly for \lstinline!elsewhen! and algorithms see below). In this case, the when-clause equations remain active during the | |
| (where \lstinline!when! may be replaced by \lstinline!elsewhen!) \lstinline!when initial() then! or \lstinline!when {$\ldots$, initial(), $\ldots$} then! (and similarly for when-statements, see below). In this case, the when-clause equations remain active during the |
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I first considered a text like that, but I didn't like it since there is a slight difference between elsewhen and when, in that when is always first - and I wanted to delay those obscure cases. The elsewhen-part below handles both.
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To me it just seems unfortunate that when/elsewhen causes a lack of symmetry that is only syntactical. This is why I ended up with the formulation suggested below (if and only if they are the first clause…) that captures the symmetry of the semantics.
| That means that any subsequent \lstinline!elsewhen initial()! has no effect, | ||
| similarly as \lstinline!when false then!. |
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Could we go as far as to speak of warnings?
| That means that any subsequent \lstinline!elsewhen initial()! has no effect, | |
| similarly as \lstinline!when false then!. | |
| A tool may warn in case an \lstinline!initial()! condition cannot activate its when-clause due to an earlier when-clause already being active during initialization. |
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I considered it, but there are (as indicated) other similar cases as well, and to me it looks odd if we discuss warnings for the obscure cases - and not for the simple ones; and thought it sufficed to say that it has no effect.
| @@ -762,6 +762,15 @@ \section{Initialization, initial equation, and initial algorithm}\label{initiali | |||
| \lstinline!when initial() then! or \lstinline!when {$\ldots$, initial(), $\ldots$} then!. In this case, the algorithmic statements within the when-statement remain active during the whole | |||
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I suppose there should be an elsewhen clarification here as well, preserving the symmetry with the when-equations?
| An active when-clause inactivates the following \lstinline!elsewhen! (similarly as for when-clauses during simulation), but apart from that | ||
| the first \lstinline!elsewhen initial() then! or \lstinline!elsewhen {$\ldots$, initial(), $\ldots$} then! is similarly active during initialization as | ||
| \lstinline!when initial() then! or \lstinline!when {$\ldots$, initial(), $\ldots$} then!. |
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Oh, maybe this was also included among the intended references of the see below above?
I think we can say this more directly, if we go back to the first sentence:
The equations of a when-clause are active during initialization, if and only if they are the first clause of the when-equation explicitly enabled with \lstinline!initial()!, …
Remove double space. Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>
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I'll merge it for now and we can then later improve the formulation. |
Closes #2636