Result

Utilities for working with the Result data type.

The Result type is a special type of enum that exists to represent the possibility of a success case (with the Ok variant), or an error case (with the Err variant). Use a Result as the return type of a function that may return an error.

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import Result from "result"

Create new Result values using Ok() and Err():

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let success = Ok("Yay!")
let failure = Err("Something bad happened")

Values

Result.isOk

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isOk : Result<t, e> -> Bool

Checks if the Result is the Ok variant.

Result.isErr

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isErr : Result<t, e> -> Bool

Checks if the Result is the Err variant.

Result.toOption

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toOption : Result<t, e> -> Option<t>

Converts the Result to an Option. The error is discarded and replaced with None.

Result.flatMap

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flatMap : (t -> Result<t, e>, Result<t, e>) -> Result<t, e>

If the Result is Ok, applies the given function to the Ok value and returns the result. Returns the unmodified Err otherwise.

Result.flatMapErr

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flatMapErr : (e -> Result<t, e>, Result<t, e>) -> Result<t, e>

If the Result is an Err, applies the given function to the Err value and returns the result. Returns the unmodified Ok value otherwise.

Result.map

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map : (t -> u, Result<t, e>) -> Result<u, e>

If the Result is Ok(x), returns Ok(fn(x)). Returns the unmodified Err otherwise.

Result.mapErr

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mapErr : (e -> Result<t, e>, Result<t, e>) -> Result<t, e>

If the Result is Err(x), returns Err(fn(x)). Returns the unmodified Ok value otherwise.

Result.mapWithDefault

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mapWithDefault : (t -> u, u, Result<t, e>) -> u

If the Result is Ok(x), returns fn(x). Returns the provided default otherwise.

Result.mapWithDefaultFn

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mapWithDefaultFn : (t -> u, e -> u, Result<t, e>) -> u

If the Result is Ok(x), returns fnOk(x). If the Result is Err(y), returns fnErr(y).

Result.or

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or : (Result<t, e>, Result<t, e>) -> Result<t, e>

If the first Result is Ok, returns the first Result. Returns the second Result otherwise.

Result.and

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and : (Result<t, e>, Result<t, e>) -> Result<t, e>

If the first Result is Err, returns the first Result. Returns the second Result otherwise.

Result.peek

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peek : (t -> a, e -> b, Result<t, e>) -> Void

If the Result is Ok(x), applies the first function to x. If the Result is Err(y), applies the second function to y.

Result.peekOk

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peekOk : (t -> a, Result<t, e>) -> Void

If the Result is Ok(x), applies the function to x.

Result.peekErr

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peekErr : (e -> b, Result<t, e>) -> Void

If the Result is Err(y), applies the function to y.