No that is a good point. Often you can use an iterator where an explicit array would also work. The issue I guess is that this puts the burden on the developer to always write generic code that when you would want to accept an Array you also need to accept a iterator like LinSpace.
Maybe this is easier to do than I currently understand? If not for regular scientists like myself I find that this would force me to make my functions far more complex than I generally would do in practice. I would often just write a signature like func(x::Vector) when I want my code to accept of Vector, but if I pass a LinSpace object to this I get a type error. I like this type of coding as it fits my model of what I want to do. The contortions I would need to do for something as basic as having a nice way to get a linear array of floating point numbers to a simple function that wants to accept a Vector seems like a wart to me. Am I missing something simple? For the builtins clearly this is not the case which is nice, but it only masks the issue of how this would be used by regular users in my opinion. On Wednesday, 21 October 2015 05:59:21 UTC-7, Jonathan Malmaud wrote: > > Gabriel, I rewrote your code to not ever explicitly convert ranges to > arrays and it still works fine. Maybe I'm not quite understanding the issue? > > function Jakes_Flat( fd, Ts, Ns, t0 = 0, E0 = 1, phi_N = 0 ) > # Inputs: > # > # Outputs: > N0 = 8; # As suggested by Jakes > N = 4*N0+2; # An accurate approximation > wd = 2*pi*fd; # Maximum Doppler frequency > t = t0 + (0:Ns-1)*Ts; > tf = t[end] + Ts; > coswt = [ sqrt(2)*cos(wd*t'); 2*cos(wd*cos(2*pi/N*(1:N0))*t') ] > temp = zeros(1,N0+1) > temp[1,2:end] = pi/(N0+1)*(1:N0)' > temp[1,1] = phi_N > h = E0/sqrt(2*N0+1)*exp(im*temp ) * coswt > return h, tf; > end > > On Wednesday, October 21, 2015 at 3:11:44 AM UTC-4, Gabriel Gellner wrote: >> >> I find the way that you need to use `linspace` and `range` objects a bit >> jarring for when you want to write vectorized code, or when I want to pass >> an array to a function that requires an Array. I get how nice the iterators >> are when writing loops and that you can use `collect(iter)` to get a array >> (and that it is possible to write polymorphic code that takes LinSpace >> types and uses them like Arrays … but this hurts my small brain). But I >> find I that I often want to write code that uses an actual array and having >> to use `collect` all the time seems like a serious wart for an otherwise >> stunning language for science. ( >> https://github.com/JuliaLang/julia/issues/9637 gives the evolution I >> think of making these iterators) >> >> >> >> For example recently the following code was posted/refined on this >> mailing list: >> >> >> >> function Jakes_Flat( fd, Ts, Ns, t0 = 0, E0 = 1, phi_N = 0 ) >> >> # Inputs: >> >> # >> >> # Outputs: >> >> N0 = 8; # As suggested by Jakes >> >> N = 4*N0+2; # An accurate approximation >> >> wd = 2*pi*fd; # Maximum Doppler frequency >> >> t = t0 + [0:Ns-1;]*Ts; >> >> tf = t[end] + Ts; >> >> coswt = [ sqrt(2)*cos(wd*t'); 2*cos(wd*cos(2*pi/N*[1:N0;])*t') ] >> >> temp = zeros(1,N0+1) >> >> temp[1,2:end] = pi/(N0+1)*[1:N0;]' >> >> temp[1,1] = phi_N >> >> h = E0/sqrt(2*N0+1)*exp(im*temp ) * coswt >> >> return h, tf; >> >> end >> >> >> >> From <https://groups.google.com/forum/#!topic/julia-users/_lIVpV0e_WI> >> >> >> >> Notice all the horrible [<blah>;] notations to make these arrays … and it >> seems like the devs want to get rid of this notation as well (which they >> should it is way too subtle in my opinion). So imagine the above code with >> `collect` statements. Is this the way people work? I find the `collect` >> statements in mathematical expressions to really break me out of the >> abstraction (that I am just writing math). >> >> >> >> I get that this could be written as an explicit loop, and this would >> likely make it faster as well (man I love looping in Julia). That being >> said in this case I don't find the vectorized version a performance issue, >> rather I prefer how this reads as it feels closer to the math to me. >> >> >> >> So my question: what is the Juilan way of making explicit arrays using >> either `range (:)` or `linspace`? Is it to pollute everything with >> `collect`? Would it be worth having versions of linspace that return an >> actual array? (something like alinspace or whatnot) >> >> >> Thanks for any tips, comments etc >> >
