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I'm new to Android development and I'm currently building my first real app. I'm trying to implement a MVVM architecture and because of that I'm having a viewModel for each fragment and each viewModel has a viewModelFactory. At least, this is how I understood it has to be.

I use the boilerplate code everyone seems to use for the factory:

Got this command: cd /some/dir; /usr/local/bin/git log --diff-filter=A --follow --format=%aI -- /some/dir/file | tail -1

I want to get the output from it.

Tried this:

my $proc2 = run 'cd', $dirname, ';', '/usr/local/bin/git', 'log', '--diff-filter=A', '--follow', '--format=%aI', '--', $output_file, '|', 'tail', '-1', :out, :err;

Nothing output.

Tried this:

my $proc2 = run , $dirname, , $output_file, <| tail -1>, :out, :err;

Git throws an error:

fatal: --follow requires exactly one pathspec

The same git command runs fine when run directly from the command line.

I've confirmed both $dirname and $output_file are correct.

git log --help didn't shed any light on this for me. Command runs fine straight from command line.

UPDATE: So if I take off the | tail -1 bit, I get output from the command in raku (a date). I also discovered if I take the pipe out when running on the command line, the output gets piped into more. I'm not knowledgeable enough about bash and how it might interact with raku's run command to know for sure what's going on.

In my XML I'm just declaring a ChipGroup as follows:

I know that several similar questions exist on this topic, but to my knowledge all of them concern an async code (wrongly) written by the user, while in my case it comes from a Python package.

I have a Jupyter notebook whose first cell is

C++23 std::optional is finally getting some very useful additions.

Since my knowledge of FP is very primitive I am wondering what is the syntax for the following two operations(that according to my googling are 2 basic monadic operations):

1. monadic bind
2. monadic return

My best guesses are:

monadic bind is transform

monadic return is just C++17 std::optional constructor(8)

I am trying to get to grips with the specifics of the (C++20) standards requirements for container classes with a view to writing some container classes that are compatible with the standard library. To begin looking into this matter I have looked up the references for named requirements, specifically around container requirements, and have only found one general container requirement called Container given by the standard. Reading this requirement has given my two queries that I am unsure about and would like some clarification on:

1. The requirement for the expression a == b for two container type C has as precondition on the element type T that it is equality comparable. However, noted later on the same page under the header 'other requirements' is the explicitly requirement that T be always equality comparable. Thus, on my reading the precondition for the aforementioned requirement is redundant and need not be given. Am I correct in this thinking, or is there something else at play here that I should take into account?

2. I was surprised to see explicit requirements on T at all: notably the equality comparable requirement above and the named requirement destructible. Does this mean it is undefined behaviour to ever construct standard containers of types failing these requirements, or only to perform certain standard library function calls on them?

Apologies if these two questions sound asinine, I am currently trying to transition my C++ knowledge from a place of having a basic understanding of how to use features to a robust understanding so that I may write good generic code. Whilst I am trying to use (a draft of) the standard to look up behaviour where possible, its verbiage is oft too verbose for me to completely understand what is actually being said.

In an attempt to seek the answer I cooked up a a quick test .cpp file to try an compile, given below. All uncommented code compiles with MSVC compiler set to C++20. All commented code will not compile, and visa versa all uncommented code will. It seems that what one naively thinks should work does In particular:

• We cannot construct any object without a destructor, though the objects type is valid and can be used for other things (for example as a template parameter!)
• We cannot create an object of vector, where T has no destructor, even if we don't attempt to create any objects T. Presumably because creating the destructor for vector tries to access a destructor for T.
• We can create an object of type vector, T where T has no operator ==, so long as we do not try to use operator ==, which would require T to have operator ==.

However, just because my compiler lets me make an object of vector where T is not equality-comparable does not mean I have achieved standards compliant behaviour/ all of our behaviour is not undefined - which is what I want I concerned about, especially as at least some of the usual requirements on the container object have been violated.

Code:

There are lots of data coming from multiple sources that I need to group based on priority, but the data quality from those sources is different - they may be missing some data. The task is to group that data into a separate table, in as complete as possible way.

For example:

I recently learned there seem to be multiple ways to display an image on a web page.

The first way is to directly assign the URL to an image element's URL

I so enjoy the low boilerplate of raku OO that I am a little surprised that I cannot shake off some integration layer boilerplate.

Here is what I have working today (somewhat golfed):