## 602 Reputation

17 years, 81 days
Phd.
Paris, France

## MaplePrimes Activity

### These are replies submitted by sasomao

The problem is that if I let maple to do the explicit sum I've not a symbolic and compact answer because I can't "recognize" the summation terms (this will be excessively time expensive, nearly that do the calculus by hand!!!). On the other hand if I use the add command, maple don't expand the summation, and there is no simplifications!)
Obviously I've reversed the role of "add" and "sum" About the use of add ad sum: if I create this array: Riemann:=Array(1..4,1..4,1..4,1..4,(i,j,k,m)->add(add(''eta''[A,B]*('doublederivcov'(Z(X[])[A],Chris(X[]),i,k)*'doublederivcov'(Z(X[])[B],Chris(X[]),j,m) -doublederivcov'(Z(X[])[A],Chris(X[]),j,k)*'doublederivcov'(Z(X[])[B],Chris(X[]),i,m)),A=1..6),B=1..6)) it work. But if I do the same declaration with sum (or Sum) at the place of the two "add", maple print Error, bad index into Array So, how can I do create an array which entries are unevalued sum, without bad index error? Thank you S.V.

The problem is that if I let maple to do the explicit sum I've not a symbolic and compact answer because I can't "recognize" the summation terms (this will be excessively time expensive, nearly that do the calculus by hand!!!). On the other hand if I use the add command, maple don't expand the summation, and there is no simplifications!)
Obviously I've reversed the role of "add" and "sum" About the use of add ad sum: if I create this array: Riemann:=Array(1..4,1..4,1..4,1..4,(i,j,k,m)->add(add(''eta''[A,B]*('doublederivcov'(Z(X[])[A],Chris(X[]),i,k)*'doublederivcov'(Z(X[])[B],Chris(X[]),j,m) -doublederivcov'(Z(X[])[A],Chris(X[]),j,k)*'doublederivcov'(Z(X[])[B],Chris(X[]),i,m)),A=1..6),B=1..6)) it work. But if I do the same declaration with sum (or Sum) at the place of the two "add", maple print Error, bad index into Array So, how can I do create an array which entries are unevalued sum, without bad index error? Thank you S.V.

## Hi, thank you for the...

Hi, thank you for the reply, your second idea seem to be very good But suppose I've already declared the array Tent somewhere in the page, and also assigned the entries: Tent:= Array(1..6, [1,2,3,4,5,6]) now, if I want to reassign the entries with your metod Tent := Array(1..7, i->unapply(christoffel[i]+v^i,v)); I re-create the Tent array. There is no way to assign only the entries without still create Tent, using no loop? tk you for your help S.

## Hi, thank you for the...

Hi, thank you for the reply, your second idea seem to be very good But suppose I've already declared the array Tent somewhere in the page, and also assigned the entries: Tent:= Array(1..6, [1,2,3,4,5,6]) now, if I want to reassign the entries with your metod Tent := Array(1..7, i->unapply(christoffel[i]+v^i,v)); I re-create the Tent array. There is no way to assign only the entries without still create Tent, using no loop? tk you for your help S.

## Tk you for the help So I've...

Tk you for the help So I've created a folder inside "lib" and I've added this address with the line: savelibname:= .../lib/newdossier; and this seems to work. A question: I've to add this address any time I open maple, or the program remember it? Tk you S.

## Tk you for the help So I've...

Tk you for the help So I've created a folder inside "lib" and I've added this address with the line: savelibname:= .../lib/newdossier; and this seems to work. A question: I've to add this address any time I open maple, or the program remember it? Tk you S.
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