Confusing alternative definition of a function

Asked Jun 20 '16 at 02:31

Active Jun 20 '16 at 11:24

Viewed 74 times

I saw a function defined something like the following:

f[n_Integer][r, θ] = Sin[n r π/L] Cos[n r L π θ/4]

My question is, why did my professor define the function like above, instead of using f[n_Integer, r_, θ_]? What is the difference? I could not find any answers on Mathematica, or google, or here.

If this has been asked before,and I did not find it, I apologize.

edited Jun 20 '16 at 11:24

m_goldberg

107,779
16
103
257

asked Jun 20 '16 at 02:31

Shinaolord

4

Related concepts: Currying, Subvalues. But just for calculation purposes, no big difference. – vapor Jun 20 '16 at 03:00
3

So now you can use f[1]@@@something, while if you use the latter definition, you can only use f[1,#1,#2]&@@@something – Wjx Jun 20 '16 at 03:12
1

@Wjx, or f[1, ##] & @@@ something, if wanted. But, f[1] @@ something can be cleaner in some cases. – J. M.'s missing motivation Jun 20 '16 at 03:17
3

It's like $f_n(r,\theta)$ instead of $f(n,r,\theta)$ in mathematics. She or he is thinking of $n$ in a qualitatively different way (as parametrizing a sequence of functions, most likely). – Michael E2 Jun 20 '16 at 03:49
@J.M. yep~that'll be better :) – Wjx Jun 20 '16 at 03:59
1

did he use underscores on r,theta? As is its hard to see the point – george2079 Jun 20 '16 at 10:41
1

The form you give is an alternative to f[n_Integer, r, θ] not f[n_Integer, r_, θ_] – m_goldberg Jun 20 '16 at 11:32
4

Proposed duplicate: (7999). Recommended reading: (544), (5686494), (56504) – Mr.Wizard Jun 20 '16 at 12:29
Thanks all. And yes he used the underscores like I had in the original – Shinaolord Jun 20 '16 at 20:17
Also , I thought always when defining functions, we used underscores? What does this do differently when not using them in the example above? – Shinaolord Jun 20 '16 at 20:29
@user57404. It forces you to always write exactly[r, θ] to get the evaluator to use the this particular definition. As Michael E2 noted, object seems to be to implement indexing on f. – m_goldberg Jun 21 '16 at 00:29

Confusing alternative definition of a function

0 Answers0