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I'm a retired mathematics professor who's used numerous programming languages over the years, including FORTRAN, Pascal, and APL. My current programming interests are Mathematica and J (the jsoftware.com free product), both of which I've used in teaching.


1d
comment Implementing efficient multiple undo
Now that Mathematica 10 has been released, note that among new features is: "Computation-aware multiple undo The problem of multiple undo in Mathematica has been solved!". See wolfram.com/mathematica/new-in-10/for-existing-users.
Jul
6
comment Plotting a multivariable function
I was going to down-vote this since it would seem to be a very simple error that would be avoided by just looking at the documentation for Plot3D. Turns out, though, that it's not so easy to find an example in the documentation like this, where first one defines the function of two variables and then plots it. (The first example there of this kind is, in fact, much more complicated: NDSolve[{D[u[t, x], t] == D[u[t, x], x, x], u[0, x] == 0, u[t, 0] == Sin[t], u[t, 5] == 0}, u, {t, 0, 10}, {x, 0, 5}] followed by what is essentially Plot3D[Evaluate[u[t, x] /. %], {t, 0, 10}, {x, 0, 5}].
Jul
2
awarded  Curious
Jul
1
comment “not a list of numbers” and “cannot be used for replacing ”
For different colored curves, wrap the first argument of the Plot expression with Evaluate[...].
Jun
29
comment Kernel quits upon evaluation of a limit
In Mathematica 9.0.1 under OS X 10.9.3, I don't get a crash; as output I just get the original limit unevaluated.
Jun
29
comment Kernel quits upon evaluation of a limit
In Mathematica Programming Cloud, hence presumably in forthcoming Mathematica 10, Limit[(1 + t/Sqrt[n])^-n, n -> Infinity] just returns unevaluated without crashing. Adding Assumptions -> t > 0 gives limit 0; t < 0 gives limit Infinity; and of course t == 0 gives limit 1.
Jun
27
comment Which functions automatically generate new functions?
@Szabolcs: Yes, such examples as indicated in these comments indicate greater availability of such built-in functions. It's so much nicer, e.g., to use such functions in Postfix notation than to construct a corresponding pure functions. E.g., ints = RandomInteger[{2, 100}, 50]; ints // Select[PrimeQ] rather than ints // Select[#, PrimeQ] &.
Jun
27
comment Which functions automatically generate new functions?
@Oleksandr R.: Yes, I'm aware that one can define such function-generating functions as a user; in fact, I have certainly done so because it's such a useful thing in some situations. That's why I was looking for more built-in functions of this type.
Jun
27
comment Which functions automatically generate new functions?
@Szabolcs: Except for Derivative, I didn't recall other built-in functions that produce functions as output; nor built-in functions that, if one omits trailing arguments, yield functions as output. Such functionality is powerful, so I want to find out about other examples.
Jun
26
asked Which functions automatically generate new functions?
Jun
26
comment What is the relationship between Mathematica and Wolfram Desktop?
I have the uncomfortable feeling that, for some potential customers, choosing a Wolfram product will be like choosing within the line of one brand of dishwasher detergent: lemon scented, unscented, regular, high-efficiency, with added bleach, with added drying agent, etc. My own tendency when confronted with so many choices is to just run away.
Jun
26
comment What is the relationship between Mathematica and Wolfram Desktop?
After reading here and on the Wolfram site, it's clear that WRI has done a really poor job in explicating the differences between, and the relationships among, all these new and old products.
Jun
26
comment What is the relationship between Mathematica and Wolfram Desktop?
If Wolfram Desktop will include a local kernel, as the answer indicates, then does this mean that this product is, in effect, a superset of Mathematica? (A superset that happens to come for free, or perhaps at some lower that Mathematica itself, if you subscribe to an appropriate level of one of the Cloud products.)
Jun
16
revised Plot roots of B(z) according to angle small to large
Added version with fancier graphics including tooltips.
Jun
16
answered Plot roots of B(z) according to angle small to large
Jun
10
comment Numerical evaluation of a sum
And there is a well-known ("Calculus II") Alternating Series Test whose proof implies that, for an alternating series whose terms have absolute values that decrease and approach 0, the (mathematical) truncation error in using the *n*th partial sum does not exceed the magnitude of the next term.
Jun
8
revised Numerical evaluation of a sum
Explicitly added step taking N, per suggestion of @eldo.
Jun
7
comment Numerical evaluation of a sum
@eldo: OK, I made my comment into an answer.
Jun
7
answered Numerical evaluation of a sum
Jun
7
comment Numerical evaluation of a sum
This doesn't directly answer the original question, but why not use the fact that Mathematica can evaluate the exact sum symbolically: Sum[(-1)^n/n^3, {n, 1, Infinity}] gives (-3*Zeta[3])/4. You may then use N, with a 2nd argument to specify the desired precision.