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overriding variables depends on position of variable assignment
  Rank: Advanced Member Groups: Registered
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Hello, found a bug in variable assignment. If I assign a number to a variable before I define the equation, I cannot override it later. It seems, the variable is handled as a constant. If I first define the equation and after that assign the variable I can override it. This is a big error source! Open in SMath CloudEdited by user 30 September 2012 17:33:27(UTC)
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  Rank: Administration Groups: Registered, Advanced Member Joined: 23/06/2009(UTC) Posts: 1,740   Was thanked: 318 time(s) in 268 post(s)
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Hello, Pay attention on this. It is correct. Just hoover the mouse over a:=b+c and x:=y+z and you will see the difference, see their symbolic results, or press a or x wherever you want (The Dynamic Assistance will give you their definition) and you will see that how these variables are defined and why behave differently. a=b+cx=5+zRegards, Radovan Edited by user 30 September 2012 18:04:33(UTC)
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When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!" |
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Joined: 15/04/2012(UTC) Posts: 1,986  Was thanked: 1124 time(s) in 721 post(s)
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Hi,
it is still a bug. Equal looking statements should produce equivalent results. Assignment with and without preceeding symbolic simplification shoukd have different operators. The same for displaying results.
And given the unreliable state of the symbolic engine, numeric optimization should be the default.
Best regards, Martin Kraska |
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Rank: Administration Groups: Registered, Advanced Member Joined: 23/06/2009(UTC) Posts: 1,740 Was thanked: 318 time(s) in 268 post(s)
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Hello Martin, Originally Posted by: mkraska  it is still a bug. Equal looking statements should produce equivalent results. Assignment with and without preceeding symbolic simplification shoukd have different operators. The same for displaying results.
And given the unreliable state of the symbolic engine, numeric optimization should be the default. You might be right about it. I can not say that this is a bug, only just the way SMath is working and trying to accept this feature. On the other hand, many times here on the Forum the SMath symbolic engine was criticized of its unreliability and problematic behavior. One of the most recent you already mentioned in this topc Help with 'for' loops ... . You also wrote in this post Originally Posted by: mkraska Would be interesting to know Andrey's priority level of this problem. I guess that debugging the symbolic engine is far from being fun. My hope is that there is at least a chance to have the visual markup of symbolic/numeric optimization resolved. Otherwise one cannot trust printed SMath sheets, as Laurence's example again demonstrated. I even would ask for a global preference setting to numeric evaluation. Many of us were quite often confused with SMath symbolic engine. I myself also reported many of my confusions about it. Some of them were corrected and some of them were not. I might be totally wrong, but I had the impression that when something gets corrected, something else got broken. Based on following the SMath developing in past few years, I suppose the main problem might be that SMath core is a symbolical engine, and the numerical things are like a "patch" to it. Just my point of view IMHO. I am not a programmer, and I know that Andrey is doing his best to make this symbolic engine to work as better as possible. Moreover, I have the impression that most of us SMath users are more numerically oriented and this is our primer focus. I would also like that SMath default behavior is much more numerically oriented, but have no idea how this could be possible. The only detailed explanation and answer to this questions can give us only Andrey himself. Regards, Radovan Edited by user 01 October 2012 12:08:21(UTC)
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When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!" |
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Rank: Advanced Member Groups: Registered
Joined: 15/04/2012(UTC) Posts: 1,986 Was thanked: 1124 time(s) in 721 post(s)
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Hello Radovan, may be, calling a particular aspect of the visual appearance a bug was really harsh. Of course I know that SMath is free and it is up to Andrey to make design decisions. I would not say that I do not care symbolic capabilities. However, as long as my 17 years old TI92 with 128k of memory by far outperforms SMath symbolically, I'll use it instead of SMath for such stuff. I guess that also the other users are not overly numeric-minded but just realize that symbolics is a mine field in SMath. The one and only reason for using software like SMath and MathCAD is the 2D natural math notation self documenting document format. If I want a program that makes things which I don't see, than I have Excel. Therefore the issue with unvisible optimization settings is quite painful. I pray for a global settings entry "Optimization", just as for decimal digits. I would set that to "numeric" and get rid of quite some problems. When I recently startet teaching Mechanics I was looking for a tool that I could recommend to my students. The options were - MathCAD. The scholl could afford the lab license, thus it would be possible. However, the students have to pay considerably for temporary licenses.
- SMath, which looked promising (and still does). I can accept bugs and limitations. Deliberate design decisions that weaken the self documenting format by hiding important settings from the user would make me revise my decision. Still I would use it as a units calculator.
- Maxima, which is favoured by colleagues at our school. For me, it is a scientific tool, not an engineering one, just like matlab, scilab, octave.
- a decent TI CAS calculator with companion PC software. They seem to infiltrate school in germany and not far in the future my students will all have one. They still base on good old derive, which was the first CAS I got hands on in the early 90s.
From time to time I ask myself if I can still justify encouraging the students to get hands on SMath. In particular that happens when I am trying to write a handbook section on programming in smath. Up to now I have no consistent description for what the effects of symbolic and numeric optimization are and how they interact with eval and line functions. Let alone their name space side effects. I feel uncomfortable with teaching things that I do not understand. For the time being I thank Andrey for developing the program and hope that the SMath cathedral won't crash. Best regards, Martin Kraska |
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I like SMath because it is an application to create readable documents, it makes it easy to share ideas with other colleagues because it is freeware, light/portable and has has a mobile version. I never get used to Matlab because I like the way msExcel works: everything is plain to see, you make a change on your worksheet and everything is recalculated, it has beautiful graphing options, and you can embed your works on msWord. I think SMath should focus on nice ways of displaying your docs, with great graphing capabilities like one of its payware competitors on android, http://www.mathstudio.net/with a good link to msexcel and openoffice calc, it should be like a document processor allowing anyone to write a thesis or project and export it to LaTeX, maybe using MathJax ? (this web application to handwrite LaTeX makes use of MathJax) Something that I dislike from SMath is that your results seem to depend on the number of 'decimal places' the user sets in configuration, and the fact that your documents get cluttered when they are opened on some other computer (something related to screen resolutions). I'd like also that the project got more revenue, that's why I proposed crowdfundingBy the way, currently the software Mathematica seems to be the most powerful as for symbolical calculations. Edited by user 02 October 2012 13:59:43(UTC)
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Rank: Advanced Member Groups: Registered
Joined: 10/11/2010(UTC)
Posts: 37
Location: Germany
Was thanked: 1 time(s) in 1 post(s)
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I think, if there's no way to change the behavier of SMath, there should be at least an error message like "redefinition of this variable not possible - already defined".
I don't want to check all calculations by a calculator, just to be sure SMath works as expected.
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overriding variables depends on position of variable assignment
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