A "syntax"/notation problem
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Author:  Dmitry [ Thu Jan 16, 2014 10:46 am ]
Post subject:  A "syntax"/notation problem

Version 3-1-6 gives me:
> 3x^2-3*x^2;

(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?


Author:  gorzel [ Thu Jan 16, 2014 6:47 pm ]
Post subject:  Re: A "syntax"/notation problem

Dmitry wrote:
Version 3-1-6 gives me:
> 3x^2-3*x^2;

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: ... .htm#SEC13

But see Section
6.4 Miscellaneous oddities
2. monomials and precedence

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.

Author:  Dmitry [ Sun Jan 19, 2014 8:17 am ]
Post subject:  Re: A "syntax"/notation problem

ok, thanks :D

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