outcome - v4.0.0

outcome

Types

ContextStack

</>

A list of context entries

pub type ContextStack =
  List(String)

Outcome

</>

An alias for the Result type. Where the error type is Problem.

pub type Outcome(t, err) =
  Result(t, Problem(err))

Problem

</>

The error type in a result ie. Result(t, Problem(e))

pub type Problem(err) {
  Problem(error: err, stack: ContextStack)
}

Constructors 

  • Problem(error: err, stack: ContextStack)

Values

context

</> 
pub fn context(
  outcome outcome: Result(a, Problem(b)),
  context context: String,
) -> Result(a, Problem(b))

Add context to a Problem. This will add a context entry to the stack.

Example

Error("Something went wrong")
|> outcome.outcome
|> outcome.context("In find user function")

map_error

</> 
pub fn map_error(
  outcome: Result(a, Problem(b)),
  mapper: fn(b) -> b,
) -> Result(a, Problem(b))

Map the error value

new_problem

</> 
pub fn new_problem(error: a) -> Problem(a)

Create a Problem Use this if you need the Problem type only. Usually you will use outcome instead.

Example

outcome.new_problem("Something went wrong")

outcome

</> 
pub fn outcome(result: Result(a, b)) -> Result(a, Problem(b))

Convert Result(a, e) to Result(a, Problem(e))

Example

Error("Something went wrong")
|> outcome.outcome

pretty_print

</> 
pub fn pretty_print(
  problem: Problem(a),
  to_s: fn(a) -> String,
) -> String

Pretty print a Problem, including the stack. The latest problem appears at the top of the stack.

Example

let result = Error("Something went wrong")
|> outcome.outcome
|> outcome.context("In find user function")
|> outcome.context("More context")

case result {
  Error(problem) ->
    outcome.pretty_print(function.identity)

  Ok(_) -> todo
}

Something went wrong

stack:
 In find user function
 More context
</> 
pub fn print_line(
  problem: Problem(a),
  to_s: fn(a) -> String,
) -> String

Print problem in one line

Example

let result = Error("Something went wrong")
|> outcome.outcome
|> outcome.context("In find user function")

case result {
  Error(problem) ->
    outcome.print_line(function.identity)

  Ok(_) -> todo
}

Something went wrong < In find user function

remove_problem

</> 
pub fn remove_problem(
  outcome: Result(a, Problem(b)),
) -> Result(a, b)

Remove the Problem wrapping in the error value

Example

let outcome = Error("Fail") |> outcome.outcome

outcome.remove_problem(outcome) == Error("Fail")
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