I agree with
On Wednesday, August 31, 2016 at 3:26:22 AM UTC+10, Chris Rackauckas wrote: > > Even then, creating the 5x5 dense matrix to then copy it into A[1:5,1:5] > is not what you'd want to do. Ideally would just have eye(5) return > something like I which has a size, and just sets A[i,j]=1 if i=j 0 > otherwise, with checks that it's the right size. Actually, the current I > would do it if you defined a dispatch on setindex!. You still don't need > the dense matrix there... > > Tim Holy had the only example where you need the dense matrix, and it's > when you want to make a dense matrix to start with and them modify the off > diagonals of that same matrix. Even then, collect(eye(5)) where eye > returned some smart type instead of a matrix wouldn't be bad syntax to do > so, and it would be consistent with the rest of the library. > > I agree that there can be a teaching problem with Julia. A lot of things > happen like fast magic to "mathematicians not trained in CS". I don't think > the right way to go is to fill Base with methods that shouldn't be used in > most cases: someone could make their own "helper libraries" if they really > think it's an issue (another example is "EasyFloats" which are not type > stable, so they will just turn into complex numbers when needed like in > MATLAB. It might help new users from MATLAB see less errors, but I'd never > want to see it in Base.) Instead I think it comes down to documentation and > extensive tutorials to fix the problem (and filling up StackOverflow with > answers). > > On Tuesday, August 30, 2016 at 10:15:08 AM UTC-7, Christoph Ortner wrote: >> >> >> If this is your only use-case of I, then you don't need it anyways. Just >> write 1.0 * A instead; same effect, independent of what type of array A is. >> >> But what if I use I in a different way? Suppose I want to A[1:5,1:5] = >> eye(5); I can't do that with I. Of course we could give it another type >> parameters, and then do the whole collect thing again. But then we are back >> to what I said before above about needless distractions. >> >> I don't understand why there is such a resistance to providing both the >> explicit arrays and the lazy functionalities in Julia. >> >> Christoph >> >> >> On Tuesday, 30 August 2016 17:32:37 UTC+1, Júlio Hoffimann wrote: >>> >>> I don't think there is anything like pushing the language to computer >>> scientists, it's the exact opposite, making it seamlessly fast without >>> forcing the user to manipulate types. Again, you write B = I*A and get B = >>> copy(A) performance. That is the original proposal. >>> >>> Most of us follow the same development strategy while doing science, we >>> write something quick and profile later. The fact that Julia can be fast >>> from the beginning is the best thing about it, no need for rewriting code. >>> >>> -Júlio >>> >>
