Result fold's in gleam

[tearaj]

Hey, I am a newbie in gleam, i was trying to solve a scenario where i have a result object and based on whether the result is Ok or Error, i would perform a addition operation, below is the snippet of code

  let occurances = get_occurances(num_list)
  use acc, item <- list.fold(num_list, 0)
  case dict.get(occurances, item) {
    Ok(occured_times) -> {
      acc + { item * occured_times }
    }
    _ -> acc
  }

i was looking into how to change the case dict.get into a piping operation using the result library, something like

 dict.get(occurances, item)
   |> result.map(fn(occ_time) { acc + { item * occ_time } })

but i was facing issues trying to figure out how to perform the operation during the error case when the key doesnt exist in the Dict. I tried using map_error, but that wraps the output i want inside the Error() and not what i want. This is what i tried

    dict.get(occurances, item)
    |> result.map(fn(occ_time) { acc + { item * occ_time } })
    |> result.map_error(fn(_){acc})

My question is if there is any way to write the above like
result.fold(result_object, on_error_function, on_ok_function)
the above was inspired from the Arrow.kt library in Kotlin.

Please let me know if there is a way to achieve what i want

[lpil]

I would write it with a case expression, but without use. I believe this would be the easiest to understand code.

[tearaj]

Thanks for responding Ipil!
I get that it would be easier to understand it without the use, (i was trying to figure out all possible ways to make use of use).
And i wanted to understand if there is a way to maybe make use of the result library to perform some function if the result is an error and some other if the result is a success, like if there was some built in way to do that without using case expressions

[lpil]

You could use map with unwrap perhaps.

[tearaj]

thank you!