Creating Results

Now that you understand the Result type, let's learn how to create them using the library's helper functions.

Creating Success Results with `succeed`

The succeed function creates a Success result:

import { import ResultResult } from '@praha/byethrow';

// With a value
const const success: Result.Result<42, never>success = import ResultResult.const succeed: <42>(value: 42) => Result.Result<42, never> (+1 overload)succeed(42);
// Type: Result.Result<number, never>

// Without a value (void)
const const voidSuccess: Result.Result<void, never>voidSuccess = import ResultResult.const succeed: () => Result.ResultFor<never, void, never> (+1 overload)succeed();
// Type: Result.Result<void, never>

With Async Values

If you pass a Promise, succeed automatically returns a ResultAsync:

import { import ResultResult } from '@praha/byethrow';

const const asyncSuccess: Result.ResultAsync<string, never>asyncSuccess = import ResultResult.const succeed: <Promise<string>>(value: Promise<string>) => Result.ResultAsync<string, never> (+1 overload)succeed(var Promise: PromiseConstructorRepresents the completion of an asynchronous operationPromise.PromiseConstructor.resolve<string>(value: string): Promise<string> (+2 overloads)Creates a new resolved promise for the provided value.
@paramvalue  A promise.@returnsA  promise whose internal state matches the provided promise.resolve('hello'));
// Type: Result.ResultAsync<string, never>

const const resolved: Result.Result<string, never>resolved = await const asyncSuccess: Result.ResultAsync<string, never>asyncSuccess;
// Type: Result.Result<string, never>

Creating Failure Results with `fail`

The fail function creates a Failure result:

import { import ResultResult } from '@praha/byethrow';

// With an error value
const const failure: Result.Result<never, "Something went wrong">failure = import ResultResult.const fail: <"Something went wrong">(error: "Something went wrong") => Result.Result<never, "Something went wrong"> (+1 overload)fail('Something went wrong');
// Type: Result.Result<never, string>

// Without a value (void)
const const voidFailure: Result.Result<never, void>voidFailure = import ResultResult.const fail: () => Result.ResultFor<never, never, void> (+1 overload)fail();
// Type: Result.Result<never, void>

With Async Errors

Like succeed, if you pass a Promise, fail returns a ResultAsync:

import { import ResultResult } from '@praha/byethrow';

const const asyncFailure: Result.ResultAsync<never, string>asyncFailure = import ResultResult.const fail: <Promise<string>>(error: Promise<string>) => Result.ResultAsync<never, string> (+1 overload)fail(var Promise: PromiseConstructorRepresents the completion of an asynchronous operationPromise.PromiseConstructor.resolve<string>(value: string): Promise<string> (+2 overloads)Creates a new resolved promise for the provided value.
@paramvalue  A promise.@returnsA  promise whose internal state matches the provided promise.resolve('async error'));
// Type: Result.ResultAsync<never, string>

const const resolved: Result.Result<never, string>resolved = await const asyncFailure: Result.ResultAsync<never, string>asyncFailure;
// Type: Result.Result<never, string>

Starting a Pipeline with `do`

The do function is a convenient way to start a pipeline with an empty object:

import { import ResultResult } from '@praha/byethrow';

const const start: Result.Result<{}, never>start = import ResultResult.function do(): import("/home/runner/work/byethrow/byethrow/packages/byethrow/dist/esm/result").Result<{}, never>
export do
Alias for succeed({}). Commonly used as a neutral base value in functional chains or monadic pipelines.
@function@exampleimport { Result } from '@praha/byethrow';

const result = Result.do();
// Result.Result<{}, never>
@categoryCreatorsdo();
// Type: Result.Result<{}, never>

This is especially useful when building up an object step by step (we'll cover this pattern with bind in a later section):

import { import ResultResult } from '@praha/byethrow';

const const result: Result.Result<{
    name: "Alice";
    age: 30;
}, never>
result = import ResultResult.const pipe: <Result.Result<{}, never>, Result.Result<{
    name: "Alice";
}, never>, Result.Result<{
    name: "Alice";
    age: 30;
}, never>>(a: Result.Result<{}, never>, ab: (a: Result.Result<{}, never>) => Result.Result<{
    name: "Alice";
}, never>, bc: (b: Result.Result<{
    name: "Alice";
}, never>) => Result.Result<{
    name: "Alice";
    age: 30;
}, never>) => Result.Result<{
    name: "Alice";
    age: 30;
}, never> (+25 overloads)
pipe(
  import ResultResult.function do(): import("/home/runner/work/byethrow/byethrow/packages/byethrow/dist/esm/result").Result<{}, never>
export do
Alias for succeed({}). Commonly used as a neutral base value in functional chains or monadic pipelines.
@function@exampleimport { Result } from '@praha/byethrow';

const result = Result.do();
// Result.Result<{}, never>
@categoryCreatorsdo(),
  import ResultResult.const bind: <"name", Result.Result<{}, never>, Result.Result<"Alice", never>>(name: "name", fn: (a: {}) => Result.Result<"Alice", never>) => (result: Result.Result<{}, never>) => Result.Result<{
    name: "Alice";
}, never> (+1 overload)
bind('name', () => import ResultResult.const succeed: <"Alice">(value: "Alice") => Result.Result<"Alice", never> (+1 overload)succeed('Alice')),
  import ResultResult.const bind: <"age", Result.Result<{
    name: "Alice";
}, never>, Result.Result<30, never>>(name: "age", fn: (a: {
    name: "Alice";
}) => Result.Result<30, never>) => (result: Result.Result<{
    name: "Alice";
}, never>) => Result.Result<{
    name: "Alice";
    age: 30;
}, never> (+1 overload)
bind('age', () => import ResultResult.const succeed: <30>(value: 30) => Result.Result<30, never> (+1 overload)succeed(30)),
);
// Type: Result.Result<{ name: string; age: number }, never>

References

Function	Purpose
succeed(value)	Create a success result
fail(error)	Create a failure result
do()	Start with empty object

#Creating Results

#Creating Success Results with succeed

#With Async Values

#Creating Failure Results with fail

#With Async Errors

#Starting a Pipeline with do