Isn't it or is it not?
-
It matters in higher-level stuff like matrix algebra, where · (dot product), × (cross product), and * (star product?) are all different.
-
When dealing with vectors, yes, there is a separate dot product and cross product. They are two different things, so they have two different operators, but also the omittment of operator is illegal. I have never seen a "star product" in my life regarding vectors.
With matrix multiplication, there's really only one way to multiply matrices, and this involves no operator signs at all. Any other is either illegal or isn't matrix multiplication.
Mind you, this is about Poland - I wouldn't be surprised if it was totally different in the even-further-than-far-east.
-
Yes. No hierarchy of operators, strict right-to-left. But....
You have to take care with this one. 40 to the -40 power is a very small number (around 8.27E-64), and most floating point hardware will evaluate 1+(40 to the -40 power) as 1
Oh, crud. You are correct. APL does not use * for multiply. Here I thought I had a fine joke, and I muffed it.
-
I wonder what happens when you get into tensors. (I bailed out of math before we got to those, so I really don't know…)
-
I did maths and physics all the way through high school and into university and never heard of tensors. Skimming the wikipedia article suggests I have done all the theory, just not used the term!
-
My keyboard has things like that by default
-
I did maths and physics all the way through high school and into university and never heard of tensors.
As I understand it, they're higher-order matrices, and are useful for describing things like rotations, spinning object, rotating vector fields, that sort of thing. I wouldn't be at all surprised if they get some funny operators of their own that make sense in 3 (or more) dimensions. Or maybe you'd use quaternions, which are a different representation of what might be about the same sort of mathematics.
It's always fun to see when people first encounter these things and find that multiplication is not necessarily commutative…
-
Such decadence
-
That's a bullet, •, not a dot, ⋅.
-
Or maybe you'd use quaternions, which are a different representation of what might be about the same sort of mathematics.
and useful for making very pretty pictures: http://paulbourke.net/fractals/quatjulia/
-
At first glance, it looked like the product of diarrhoea.
-
I wonder what happens when you get into tensors.
Tensors are fun. You have two different sets of indices (one written high, the other low; order is important so high-low-high is different from high-high-low) and an auto-summation notation - basically if you have a tensor product where an index on one tensor matches an index on the other, you take the sum over all possible values of that index.But there's no multiplication symbol.
-
But there's no multiplication symbol.
So there's no multiplication-like composition operator? (Or maybe too many of them.)
-
and useful for making very pretty pictures:
That looks like the path traced out around a strange attractor
-
It is between z an c
Internationalisation fail. Between z and c on my keyboard is a choice of s or d, or maybe both.
-
You do realise that you're also totally oppressed in that you can't use + for multiplication either. When will the mathematical fascism end?
unsigned int multiply(unsigned int a, unsigned int b){ int result=0; while(a-->0) result+=b; return result; }
-
Oh, crud. You are correct. APL does not use * for multiply. Here I thought I had a fine joke, and I muffed it.
You were on to a good thing, sure, and I almost muffed the same thing myself. It's been about 30 years since I touched anything to do with APL, so I have an excuse. That said, I still have at home a hardback textbook (about APL, duh) that I won in a competition to write APL code to rank poker hands. It may have helped that I made liberal use of the APL character⍝
, commonly called "lamp" (I heard it from guys at IBM as "thumb"). It's the equivalent of // in C++. It probably also helped that my code actually worked. (Heaven forbid...)
-
I was replying to @RaceProUK, not the whole world
-
I was replying to @RaceProUK, not the whole world
Sure, but it's still an internationalisation fail. And how do you know that @RaceProUK doesn't use a Dvorak keyboard?
-
I don't see that on my keyboard (or any keyboard I've ever used)
And yes, I know how to type it
I have, on the APL version of an IBM 3277 mainframe terminal.
-
And how do you know that @RaceProUK doesn't use a Dvorak keyboard?
Because there have been conversations about keyboard layouts repeatedly and IIRC she wasn't one of us that use it?
-
how do you know that @RaceProUK doesn't use a Dvorak keyboard?
Wouldn't you like to know? ;)