I can write:
x\_m<TAB> = 5
to get x subscript m as a variable name in Julia. What if I want to subscript a word instead of a single character? This
x\_max<TAB> = 5
doesn't work. However,
x\_m<TAB>\_a<TAB>\_x<TAB> = 5
does work, it's just very uncomfortable. Is there a better way?
As I noted in my comment, not all ASCII characters exist as unicode super- or sub-scripts. In addition, another difficulty in generalizing this tab completion will be determining what \_phi<TAB> should mean: is it ₚₕᵢ or ᵩ? Finally, I'll note that since these characters are cobbled together from different ranges for different uses they look pretty terrible when used together.
A simple hack to support common words you use would be to add them piecemeal to the Base.REPLCompletions.latex_symbols dictionary:
Base.REPLCompletions.latex_symbols["\\_max"] = "ₘₐₓ"
Base.REPLCompletions.latex_symbols["\\_min"] = "ₘᵢₙ"
You can put these additions in your .juliarc.jl file to load them every time on startup. While it may be possible to get a comprehensive solution, it'll take much more work.
Since Julia 1.6 this works for subscripts (\_) and superscripts(\^) in the Julia REPL.
x\_maxTAB will print out like this: xₘₐₓ.
x\^maxTAB will print out like this: xᵐᵃˣ.
Related
It is known that default printer can be confusing wrt lists because of no output for empty lists and 3 different notations being mixed (, vs (x;y;z) vs 1 2 3) and not obvious indentation/columnization (which is apparently optimized for table data). I am currently using -3! but it is still not ideal.
Is there a ready-made pretty-printer that has consistent uniform output format (basically what I am used to in any other language where list is not special)?
I've started using .j.j for string outputs in error messages more recently in preference to -3!. Mainly I think it is easier to parse in a text log, but also doesn't truncate in the same way.
It still transforms atoms and lists differently so it might not exactly meet your needs, if you really want that you could compose it with the old "ensure this is a list" trick:
myPrinter:('[.j.j;(),])
You might need to supply some examples to better explain your issues and your use-case for pretty-printing.
In general -3! is the most clear visual representation of the data. It is the stringified equivalent to another popular display method which is 0N!.
The parse function is useful for understanding how the interpreter reads/executes commands but I don't think that will be useful in your case
I have a method in Scala that returns a tuple, let's say the method is called 'test'. Then I want to do
val (X,Y) = test()
However, the pattern-matching only works in Scala when the variable names are lowercase, ie:
val(_X,_Y) = test(); val X = _X; val Y = _Y
... works ok, but is ugly, and not terse. Since X and Y are matrices, I don't really want to have to use lowercase variables. (In scipy and matlab, I wouldn't have such a restriction for example).
I think there is some way to make sure lowercase variables behave like uppercase ones, ie by doing `x`. Perhaps there is some way of making uppercase variables behave like lowercase ones? So, that is my question: is there some way of pattern matching directly into uppercase variables in Scala?
The short answer is don't.
Syntax conventions make your code readable and understandable for others. Scala's convention is that variables start with lower-case and constants and classes start with upper-case. By violating this, not only you get problems like pattern-matching issues, your code becomes less readable. (Believe me, if you ever have to read code written by someone else who didn't care for such conventions, you'll be cursing that person.)
If you want to emphasize that the variables are matrices, I suggest you to use xMatrix and yMatrix or something like that. This will make clear that they're variables and that they represent matrices.
Or create a convention specific to your project that all matrix variables will end with let's say "M", like xM and yM.
It's worth typing a few more characters if it makes your code readable.
There is no way to do this and there shouldn't be. You already have the type of the variable to tell you that it is a matrix, so there is no need to make variable names uppercase.
I just read the following article from MathWorks which describes why it is important to avoid the eval function and lists alternatives to many of eval's common uses.
After reading the article, I have the impression that the eval function is neither useful nor necessary. So, my question is this: When is the eval function necessary?
I have found only one useful case for eval, and then the evalc variety: when calling a function with built-in command line call back (e.g. lines without ; or with disp calls), which you cannot modify. For instance when you got some obfuscated function that dumps heaps of stuff to your command window. In that case it's best to try and obtain the source code to modify that to your needs, as using evalc will mess up your performance. Otherwise, I have not found a case where eval is the best solution.
I wrote an extensive answer detailing why you should try to avoid eval as much as possible here: How to put these images together?
I have already used eval when trying to create multiple arrays with different names. This is not really recommended, but it worked for my specific application. For example, if I wanted to have N matrices with the specific names "matrix1" "matrix2" .. "matrixN" , one solution would be to manually type these in as "matrix1 = something" ... "matrixN = somethingelse". If N is really large, this is not ideal. Using eval , you could set up a for loop that would change the name of the matrix on every loop, and calculate some value based on that same N value.
Of course, ideally saving them in to a cell would be better, but I needed the arrays in the format I described.
I apologize if this is a newb question, but I have read the documentation here and it says nothing about having to input any command before using substring.
However, when I try to call it as follows:
substring('hello world', 2)
It gives me the error
??? Undefined function or method 'substring' for input arguments of type 'char'.
What is the correct way to invoke this substring?
Not to detract from the OP's answer, which actually more directly adresses the question you ask, but assuming all you want to do is extract a certain number of characters from a string, MATLAB's indexing is all you need:
myString = 'Hello, world!';
mySubstring = myString(3:end)
mySubstring =
llo, world!
substring is not a MATLAB function at all, at least in MATLAB proper. There IS a substring JAVA function, but I have no idea if that is what you are asking.
>> which substring
substring is a Java method % java.lang.String method
The above also tells you what you will need to do. Look here. (Google is your friend. Of course, you could as easily have done exactly what I just did, and gotten this answer far more quickly.)
You may also be talking about some custom code, written by some colleague of yours. In that case, talk to your friend. Very often I hear about tools that were written by someone, then left around as legacy code, unsupported. Eventually, it just disappears due to path issues when new versions of MATLAB are installed.
You might actually want strsplit. This will parse char data by a given or default delimiter and return a cell array of the pieces.
When working with unpack, I had hoped that b3 would return a bitstring, 3 bits in length.
The code that I had hoped to be writing (for parsing a websocket data packet) was:
my($FIN,$RSV1, $RSV2, $RSV3, $opcode, $MASK, $payload_length) = unpack('b1b1b1b1b4b1b7',substr($read_buffer,0,2));
I noticed that this doesn't do what I had hoped.
If I used b16 instead of the template above, I get the entire 2 bytes loaded into first variable as "1000000101100001".
That's great, and I have no problem with that.
I can use what I've got so far, by doing a bunch of substrings, but is there a better way of doing this? I was hoping there would be a way to process that bit string with a template similar to the one I attempted to make. Some sort of function where I can pass the specification for the packet on the right hand side, and a list of variables on the left?
Edit: I don't want to do this with a regex, since it will be in a very tight loop that will occur a lot.
Edit2: Ideally it would be nice to be able to specify what the bit string should be evaluated as (Boolean, integer, etc).
If I have understood correctly, your goal is to split the 2-bytes input to 7 new variables.
For this purpose you can use bitwise operations. This is an example of how to get your $opcode value:
my $b4 = $read_buffer & 0x0f00; # your mask to filter 9-12 bits
$opcode = $b4 >> 8; # rshift your bits
You can do the same manipulations (maybe in a single statement, if you want) for all your variables and it should execute at a resonable good speed.