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Topic review - A "syntax"/notation problem
Author Message
  Post subject:  Re: A "syntax"/notation problem  Reply with quote
ok, thanks :D
Post Posted: Sun Jan 19, 2014 8:17 am
  Post subject:  Re: A "syntax"/notation problem  Reply with quote
Dmitry wrote:
Version 3-1-6 gives me:
> 3x^2-3*x^2;
6x2

Singular interprets 3x^2 as (3x)^2 which is 9*x^2, then the result 6x2 follows

Everything left from the ^ upto an * or + or - is taken as one token,
thus e.g. 2x2y^3 is 8*x^6*y^3;

Certainly a user should know this behaviour
but it seems to be a bit hidden in the manual.
Sadly, it is not stated precisely in the Getting started part:
http://www.singular.uni-kl.de/Manual/la ... .htm#SEC13

But see Section
6.4 Miscellaneous oddities
2. monomials and precedence
http://www.singular.uni-kl.de/Manual/3-1-6/sing_458.htm

To remember:
If the variable names consist only of single letters,
Singular allows to omit the * for the multiplication.
If one do so, then also one don't use the caret ^ for the exponentiation.

Conversely, if you use the long version with ^, then you should put the *, too.
Post Posted: Thu Jan 16, 2014 6:47 pm
  Post subject:  A "syntax"/notation problem  Reply with quote
Version 3-1-6 gives me:
> 3x^2-3*x^2;
6x2

(And of course this difference between 3x^2 and 3*x^2 influences other computations, e.g. Milnor number etc.)
It is difficult to always remember, especially if one works with other computer systems. Could you correct this in the future version?

Thanks!
Post Posted: Thu Jan 16, 2014 10:46 am


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