Hello, I have two questions: 1- Why can’t I assign '' to a variable? julia> ch = '' ERROR: ParseError: # Error @ REPL[17]:1:7 ch = '' # └ ── empty character literal Stacktrace: [1] top-level scope @ none:1 2- Why doesn’t Julia have a reverse for loop? for h = 10 : 1 I know that this pr…

[image] hack3rcon: 1- Why can’t I assign '' to a variable? julia> ch = '' ERROR: ParseError: # Error @ REPL[17]:1:7 ch = '' # └ ── empty character literal Stacktrace: [1] top-level scope @ none:1 This isn’t about assigning to a variable. The problem is that '' itself isn’t valid synt…

You could also write reverse(1:10), which is considered identical: julia> reverse(1:10) == 10:-1:1 true

[image] hack3rcon: Why doesn’t Julia have a reverse for loop? for h = 10 : 1 See The colon punctuation: Why doesn't 5:1 return [5, 4, 3, 2, 1]?

It would obviously be way too breaking, but I wonder if 10:1 should be 10:-1:1 and there should be a different way to ask for the empty range starting at 10. Our reasoning is principled but I don’t think anyone new to the language understands it.

Wouldn’t this be inherently type unstable? And that would be unfortunate for something so commonly used as ranges. Also, what languages actually returns a reverse unit range for 10:1? Not Matlab, and not numpy.

[image] DNF: Wouldn’t this be inherently type unstable? Right, that was discussed in the thread I linked above. (There’s also the issue of representing empty ranges like 5:4, which are useful for searches etc.)

Hello, Thank you so much for your reply. What is the use of empty range?

Hello, Please take a look at this code in C++ programming language: #include <iostream> using namespace std; int main() { for (int i = 10; i >= 1; i--) { cout << i << " "; } return 0; }

[image] hack3rcon: What is the use of empty range? The same as the use of empty strings, empty tuples, or empty vectors. They come up often when programmatically building containers in generic code.

[image] hack3rcon: Please take a look at this code in C++ programming language: [image] hack3rcon: for (int i = 10; i >= 1; i--) { That’s a semicolon loop, essentially syntactic sugar for a while loop. The syntax does not exist in many languages, which often opt instead for foreach loo…

@DNF : R reverses ranges in this fashion and I have been bitten by that several times. @hack3rcon : Another nice thing about empty ranges is that they are valid for indexing, i.e., the following works as expected (at least that’s what I would expected, see reversed ranges above): dropthree(x) = x[4:…

Two questions about Julia

New to Julia

stevengj December 18, 2024, 1:47pm 4

See The colon punctuation: Why doesn't 5:1 return [5, 4, 3, 2, 1]?

Topic		Replies	Views
Reverse UnitRange General Usage	3	627	May 30, 2021
The colon punctuation: Why doesn't 5:1 return [5, 4, 3, 2, 1]? New to Julia question , range , unitrange	8	1499	December 16, 2023
Colon / Ranges New to Julia	5	1952	December 10, 2020
ranges and `end` token Internals & Design	3	1143	November 30, 2017
Iteration reverse in for loop New to Julia	6	8467	August 8, 2020

Two questions about Julia

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