Fri 04 Jun 2004 08:06:32 AM UTC, original submission:
(1) f:=operator 'f
(1) f
Type: BasicOperator
(2) -> D(sum(f(i),i=a..x),x)
(2) f(x) Type: Expression Integer
is nonsense. The problem is in COMBF/dvdsum:
dvdsum(l, x) ==
x = retract(y := third l)@SE => 0
k := retract(d := second l)@K
differentiate(h := third rest rest l,x) * eval(f := first l, k, h)
- differentiate(g := third rest l, x) * eval(f, k, g)
+ opdsum [differentiate(f, x), d, y, g, h]
Although this -- d/dx sum_i^x f(i) = f(x) -- is a nice try, it is wrong. It seems that the order of magnitude is roughly correct, but that's about it.
Unfortunately, I do not know how to return the thing unevaluated, so I cannot fix the bug yet
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