Some bugs calling composite functions with if() or cases()

Some bugs calling composite functions with if() or cases() - Messages

#1 Posted: 11/18/2020 2:25:14 PM
Alvaro Diaz Falconi

Alvaro Diaz Falconi

992 likes in 1674 posts.

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Hi. I don't know if this is a know one. I guess they are related to the fact that functions with if can neither be derived nor integrated. Notice that seems that there are a bug in cases() too.

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Best regards.
Alvaro.
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sergio 11/18/2020 3:27:00 PM
#2 Posted: 11/18/2020 4:21:23 PM
Alvaro Diaz Falconi

Alvaro Diaz Falconi

992 likes in 1674 posts.

Group: User

... and issues in composite functions with loops.

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Best regards.
Alvaro.



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sergio 11/18/2020 4:45:00 PM
#3 Posted: 11/18/2020 4:47:05 PM
Alvaro Diaz Falconi

Alvaro Diaz Falconi

992 likes in 1674 posts.

Group: User

Wrote

... and issues in composite functions with loops.

FunctionBug2.sm (17 KiB) downloaded 31 time(s).
FunctionBug2.pdf (76 KiB) downloaded 32 time(s).

Best regards.
Alvaro.





Debugging with trace(), what I see is that when calling g, f takes phi=1, (this is the first phi=1 in the output window) but don't do the loop. Calling f isolated shows another phi=1 and subsequent values for phi.

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With for(3) gives an error, so I can't debug that. Additionally, calling with for(4) seems to have the same behavior than while.

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#4 Posted: 11/18/2020 5:48:24 PM
Jean Giraud

Jean Giraud

983 likes in 6866 posts.

Group: User

Wrote

I don't know if this is a know one. I guess they are related to the fact that functions with if can neither be derived nor integrated. Notice that seems that there are a bug in cases() too.


1. You must assign "cases" like in your last example.
2. Before Davide introduced "cases" it was a damned job integrate
unless from discrete finite differences like in the old days.
The min(x) style [undocumented] is quite smart, mostly OK Simpson.

Cheers ... Jean

Integrate Discontinuous [min(x)].sm (16 KiB) downloaded 27 time(s).

#5 Posted: 11/19/2020 8:30:09 AM
Davide Carpi

Davide Carpi

1415 likes in 2872 posts.

Group: Moderator

As I've already mentioned here and there, assignments shouldn't be made inside cases() arguments, because:

Wrote

Please be careful however, since a symbolic evaluation to show the function content or a failed evaluation with an error triggered on the conditions leads to the evalution of all the options.
In general currently is better to use cases to host just dead content (numbers, strings, variables).



This is a downside that currently can't be prevented. As you can see making the assignment outside cases() works as expected.
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