vermaseren
commented
3 years ago Hi Lorenzo,
If I understand you correctly, the statement for you is the antibracket statement. If you use: AntiBracket x1,…,xn; .sort KeepBrackets;
you will work on the f and each different f occurs only once. Only at the end of the module the contents of the brackets will be multiplied by whatever you made of the f’s.
You can start inpsecting what you have you could start with AB x1,…,xn; Print[]; .end
which will show a list of all different f’s and how many terms there are inside each bracket.
I hope this is what you are after.
Cheers
Jos
On 20 Jan 2021, at 10:55, LorenzoTancredi notifications@github.com wrote:
Hi everyone,
i have a question about the bracket statement. Assume I have an expression which is a polynomial in many variables, say x1,...,xn, where n could be very large, and that the coefficients are complicated combinations of other objects, which I'll call f(j...), so my expressions is a sum of monomials of this type
x1^j1x2^j2...xn^jnf(j1,...,jn)
To be clear, f is just a placeholder, ie f(j1,...,jn) could be itself a polynomial in other variables unrelated to the xj ec.
Now I'd like to access, as fast as possible, a list of all the f(j1,...,jn), without having to know a priori what the j1,...,jn are.
In mathematica I would do a collect and a Cases statement.
Now in form, If I knew the js, I could do I guess something like
b x1,...,xn ; .sort l tmp = expr[x1^j1...xn^jn] ;
but I don't want to have to figure out the jns a priori, as this information should be inside form already when I do "bracket". I could also use dollar variables to read the content of the brackets, doing something like
b x1,...,xn ; .sort collect fun ; .sort
and then use dollar variables to read all possible arguments of the functions "fun", but this is extremely slow for long expressions.
I imagine that, since form has internally the information about the brackets, there has to be a way to access them somewhere without doing something this convoluted? Or am I missing something obvious? I am thinking of something like activeexprnames_ but for the brackets...
maybe there is even a different/simpler solution that I don't see?
Thank you everyone for your help! Lorenzo
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LorenzoTancredi
jodavies
benruijl
Hi everyone,
i have a question about the bracket statement. Assume I have an expression which is a polynomial in many variables, say x1,...,xn, where n could be very large, and that the coefficients are complicated combinations of other objects, which I'll call f(j...), so my expressions is a sum of monomials of this type
x1^j1x2^j2...xn^jnf(j1,...,jn)
To be clear, f is just a placeholder, ie f(j1,...,jn) could be itself a polynomial in other variables unrelated to the xj ec.
Now I'd like to access, as fast as possible, a list of all the f(j1,...,jn), without having to know a priori what the j1,...,jn are.
In mathematica I would do a collect and a Cases statement.
Now in form, If I knew the js, I could do I guess something like
b x1,...,xn ; .sort l tmp = expr[x1^j1...xn^jn] ;
but I don't want to have to figure out the jns a priori, as this information should be inside form already when I do "bracket". I could also use dollar variables to read the content of the brackets, doing something like
b x1,...,xn ; .sort collect fun ; .sort
and then use dollar variables to read all possible arguments of the functions "fun", but this is extremely slow for long expressions.
I imagine that, since form has internally the information about the brackets, there has to be a way to access them somewhere without doing something this convoluted? Or am I missing something obvious? I am thinking of something like activeexprnames_ but for the brackets...
maybe there is even a different/simpler solution that I don't see?
Thank you everyone for your help! Lorenzo