pattern matching IO?

[cobordism]

Hello,
Is there any way I can use pattern matching to get a String from an IO String? I've tried, but the deeper I dig the more confused I get.
Relatedly, is there a way to have a map2 for IO? and a function IO ( IO a)) -> IO a ?

I apologise if these are easy questions. I am new at elm and got confused.
The context is that I have a function String -> String -> String and I want to read the first two arguments from a text file.

Or is there maybe even an "evil" way to just read in a String instead of IO String from a text file ?

[lue-bird]

Indeed an IO.map2 would be nice.
You can create it yourself with andThen:

ioMap2 combineAB ioA ioB =
    ioA |> IO.andThen (\a -> IO.andThen (\b -> combineAB a b))
-- in
ioMap2
    (\a b -> yourFunction a b)
    (File.open "a.txt" |> IO.exitOnError identity)
    (File.open "b.txt" |> IO.exitOnError identity)

[cobordism]

Thank you. I also just succeeded ... because I just discovered the new-api branch of this repo.
(I wish I had found that sooner. )

The instructions in the readme:

npm install -g @albertdahlin/elm-posix
elm install albertdahlin/elm-posix

gives me the older version.

What is the correct way to install the new elm-posix branch?

[lue-bird]

Pretty sure the author didn't publish it yet.
So you can either try to vendor it, stick with the current API or switch to an alternative like elm-pages-scripts (not sure how) or state-interface etc.

[cobordism]

pardon my ignorance, but what is 'vendor' as a verb?

[lue-bird]

haha I'm not a native speaker but as I understood it it basically means copy it to your project directly and build/link/... it there with your project