Warning for 2d row vectors used in context where only a 1d column vector is used could definelty be implemented as help when you get a MethodError.
See also https://github.com/JuliaLang/julia/issues/7512. Ivar kl. 16:03:46 UTC+2 mandag 21. juli 2014 skrev Leah Hanson følgende: > > I agree that the `["a" "b" "c"]` vs `["a", "b", "c"]` syntax is something > likely to catch new-to-Julia users. I have personally watched people > struggle with that. Programmers familiar with other languages take a bit to > understand the vectors vs row-matrixes thing, when they were just expecting > a list/array type. While you can read `Array{ASCIIString, 2}` in the REPL > response to `["a" "b" "c"]` (and in the `sort` error message), you have to > know that matrixes/row-matrixes exist in Julia and that we've chosen not to > interpret a row-matrix as a list. > > I'm not in favor of make `sort` work for row-matrixes. This distinction is > an important one to learn as a Julia programmer and you will continue to > encounter it. However, maybe our error messages could be a lot better. The > most magical version would be to say something like: > > ~~~ > julia> sort(lst) > > sort(lst) > ~~~ > `lst` is an Array{ASCIIString, 2}, which `sort` has no method for. > Did you mean to define `lst` as `lst = ["a", "b", "c"]`? > ~~~ > > This is most appropriate in a "I just used a row-matrix literal." context, > but for any (short) row-matrix, it could be helpful. I use C++ at work, and > this is what many of my error messages look like: the line (with line > number/file), with the problem underlined/highlighted, a brief description > of the problem, and (often) a suggestion of what I may have meant. The > suggests are literally copy-paste-able code, not a prose description. > > I find these to be very useful, especially as a less experienced C++ user. > The suggestions appear for things like "->" vs "." (when you've got the > wrong one), when you've mistyped a variable name (there's a variable of the > proper type in-scope, and you used a non-existant/other-type variable), > when you forgot to namespace a variable/function (you used `vector` but > have to use `std::vector`). > > These error messages do a great job of "I'm not going to except your > incorrect input, but I do have a solid guess about what you meant, so I'll > tell you the answer.". They are probably my favorite thing about using C++, > and I think they are the most friendly thing you can do for new users. > > -- Leah > > > > On Mon, Jul 21, 2014 at 6:01 AM, Ivar Nesje <[email protected] > <javascript:>> wrote: > >> 1. It clearly isn't. >> >> 2. It will not cause any overhead in the common case (because it would be >> a separate method in Julia). The question is whether this is a case where >> we should guess what the user intended, or force the user to fix a >> potential problem. >> >> Not sure what we could do about this though, because the distinction is >> useful and it becomes much more annoying if you discover such subtle >> differences later rather than earlier. >> >> Ivar >> >> kl. 04:19:53 UTC+2 mandag 21. juli 2014 skrev Abe Schneider følgende: >> >>> It wasn't obvious to me initially why `sort` wasn't working for me >>> (strings and composite types). On further investigation it looks like that >>> it only works for single-dimension arrays -- which makes sense. However, if >>> I type: >>> >>> lst = ["a" "b" "c"] >>> sort(lst) >>> >>> I get an error. The answer is that it's of type `Array{ASCIIString, 2}`, >>> whereas `sort` wants the type to be `Array{ASCIIString, 1}`. The correct >>> solution is to write this instead: >>> >>> lst = ["a", "b", "c"] >>> sort(lst) >>> >>> The problem seems to derive from two design decisions: >>> >>> 1. It is not obvious to someone new to Julia why one form gives a >>> two dimensional array whereas the other gives a one dimensional array. >>> 2. `sort` doesn't try to determine if the array passed is actually >>> jeust one dimensional. >>> >>> I'm not sure there is a simple solution. I assume there's a good reason >>> for (1) and (2) involves some overhead which might be undesirable. >>> >> >
