PowMaybe 0.0.5
See the version list below for details.
dotnet add package PowMaybe --version 0.0.5
NuGet\Install-Package PowMaybe -Version 0.0.5
<PackageReference Include="PowMaybe" Version="0.0.5" />
paket add PowMaybe --version 0.0.5
#r "nuget: PowMaybe, 0.0.5"
// Install PowMaybe as a Cake Addin #addin nuget:?package=PowMaybe&version=0.0.5 // Install PowMaybe as a Cake Tool #tool nuget:?package=PowMaybe&version=0.0.5
PowMaybe
Table of content
Introduction
Lightweight Maybe monad library to simplify code that can fail.
It will help you transform code like this:
Before
Person? ParsePage(string url)
{
var html = client.Query(url);
if (html == null)
return null;
var root = Html.GetRoot(html);
var node = root.SelectSingleNode("xpath query");
if (node == null)
return null;
var personInfo = Utils.ParseNode(node);
if (personInfo == null)
return null;
return new Person(personInfo);
}
Into this:
After
Maybe<Person> ParsePage(string url) =>
from html in Utils.Query(url)
let root = Utils.GetRoot(html)
from node in root.MaySelectSingleNode("xpath query")
from personInfo in Utils.MayParseNode(node)
select new Person(personInfo);
The result is:
- shorter code
- less nested
- no if conditions
- no nullable references
It will not apply for all the code everywhere, but when it does apply it will drastically reduce the potential for bugs.
Usage
Creation
var a = May.Some(47);
var b = May.None<string>();
// nullable reference -> Maybe<>
var mayPerson = person.ToMaybe();
// Maybe<> -> nullable reference
var person = mayPerson.ToNullable();
Combining
Maybe<string> QueryHtml(string url);
Maybe<Person> ParsePerson(string html);
// use any number of from/in statements with a select at the end
Maybe<Person> QueryAndParse(string url) =>
from html in QueryHtml(url)
from person in ParsePerson(html)
where person.Name != "John" // you can also use where statements
select parson;
Unwrapping
Maybe<Person> mayPerson = ...
if (mayPerson.IsSome(out var person))
{
// Success, you can access person here
}
else
{
// Failure
}
Person person = mayPerson.Ensure(); // throws an Exception if mayPerson is None
Person person = mayPerson.FailWith(peter); // returns peter if mayPerson is None
Enumerations
IEnumerable<T> WhereSome<T>(this IEnumerable<Maybe<T>> source);
Maybe<T> FirstOrMaybe<T>(this IEnumerable<T> source, Func<T, bool>? predicate = null)
// and similar LastOrMaybe
// Examples
// ========
new [] { May.Some(4), May.None<int>() May.Some(12) }.WhereSome();
// int[] { 4, 12 }
new [] { 2, 6, 5 }.FirstOrMaybe(e => e % 3 == 0)
// Some(6)
new [] { 2, 6, 5 }.FirstOrMaybe(e => e % 3 == 1)
// None<int>()
Example
Let's say you want to read your configuration from multiple sources:
- environment variables
- command line arguments
- json file
And once a source returns a configuration, you do not want to read the other sources.
You could write it this way:
Maybe<Config> ReadFromEnvVars();
Maybe<Config> ReadFromArgs(string[] args);
Maybe<Config> ReadFromFile(string file);
Maybe<Config> ReadConfig(string[] args, string file) =>
new[]
{
() => ReadFromEnvVars(),
() => ReadFromArgs(args),
() => ReadFromFile(file),
}
.Select(readFun => readFun())
.WhereSome()
.FirstOrMaybe();
License
MIT
Product | Versions Compatible and additional computed target framework versions. |
---|---|
.NET | net7.0 is compatible. net7.0-android was computed. net7.0-ios was computed. net7.0-maccatalyst was computed. net7.0-macos was computed. net7.0-tvos was computed. net7.0-windows was computed. net8.0 was computed. net8.0-android was computed. net8.0-browser was computed. net8.0-ios was computed. net8.0-maccatalyst was computed. net8.0-macos was computed. net8.0-tvos was computed. net8.0-windows was computed. |
-
net7.0
- No dependencies.
NuGet packages (5)
Showing the top 5 NuGet packages that depend on PowMaybe:
Package | Downloads |
---|---|
PowRxVar.Maybe
Composable reactive variables |
|
PowRxVar.WinForms
Composable reactive variables |
|
PowWeb
Puppeteer and Chrome DOMSnapshot API wrapper |
|
ImdbLib
IMDB scraping |
|
ParserLib
Parsing utilities |
GitHub repositories
This package is not used by any popular GitHub repositories.