[Scilab-users] expression block in xcos gives “answer given for scilab expression is wrong” error

[Samuel Gougeon]

Hello Farimani,

Le 19/02/2019 à 10:47, farimani a écrit :
> As I have originally explained in  this post
> <https://stackoverflow.com/questions/54756985/expression-block-in-xcos-gives-answer-given-for-scilab-expression-is-wrong-err>
> I'm trying to put the SciLab expression:
>
> sign(u2 – u1) * (2 * ((Fm + M) * abs(u2 – u1) + k * (u2^2 – u1^2) / 2) /
> m)^0.5
>
> but I get this error message:
>
> <http://mailinglists.scilab.org/file/t497909/7ivdz.png>
>
> answer given for scilab expression is incorrect...
>
> I would appreciate if you could help me know what is the problem and how I
> can solve it. Maybe I should use a different block?

Copy/pasting your formula in the console:

[Fm,  M,  m,  k]  =  (1,1,1,1);
[u1,  u2]  =  (1,2);
r  =  sign(u2  –  u1)  *  (2  *  ((Fm  +  M)  *  abs(u2  –  u1)  +  k  *  (u2^2  –  u1^2)  /  2)  /m)^0.5; --> r = sign(u2 – u1) * (2 * ((Fm + M) * abs(u2 – u1) + k * 
(u2^2 – u1^2) / 2) /m)^0.5;r = sign(u2 – u1) * (2 * ((Fm + M) * abs(u2 – 
u1) + k * (u2^2 – u1^2) / 2) /m)^0.5;^~~^Error: syntax error, unexpected 
identifier, expecting "," or )

Puzzling... Hard to find why, but finally:

You have likely copy/pasted this formula from a "formatted" document, 
maybe a web site, etc.
Then, the included "–" character is not the mathematical minus, that is "-".
This puzzles the Scilab's parser.

If you input the same formula, just replacing the hyphens with the true 
minus, it works,
in the console as well as in Xcos.

--> r = sign(u2 - u1) * (2 * ((Fm + M) * abs(u2 - u1) + k * (u2^2 - 
u1^2) / 2) /m)^0.5
  r  =
    2.6457513

HTH
Samuel

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