You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
105 lines
4.4 KiB
105 lines
4.4 KiB
using System;
|
|
using System.Collections;
|
|
using System.Collections.Generic;
|
|
using System.Linq;
|
|
using System.Text;
|
|
using System.Threading.Tasks;
|
|
|
|
namespace IPA.Utilities
|
|
{
|
|
/// <summary>
|
|
/// Extensions for <see cref="IEnumerable{T}"/> that don't currently exist in <c>System.Linq</c>.
|
|
/// </summary>
|
|
public static class EnumerableExtensions
|
|
{
|
|
/// <summary>
|
|
/// Adds a value to the beginning of the sequence.
|
|
/// </summary>
|
|
/// <typeparam name="T">the type of the elements of <paramref name="seq"/></typeparam>
|
|
/// <param name="seq">a sequence of values</param>
|
|
/// <param name="prep">the value to prepend to <paramref name="seq"/></param>
|
|
/// <returns>a new sequence beginning with <paramref name="prep"/></returns>
|
|
public static IEnumerable<T> Prepend<T>(this IEnumerable<T> seq, T prep)
|
|
=> new PrependEnumerable<T>(seq, prep);
|
|
|
|
private sealed class PrependEnumerable<T> : IEnumerable<T>
|
|
{
|
|
private readonly IEnumerable<T> rest;
|
|
private readonly T first;
|
|
|
|
public PrependEnumerable(IEnumerable<T> rest, T first)
|
|
{
|
|
this.rest = rest;
|
|
this.first = first;
|
|
}
|
|
|
|
public IEnumerator<T> GetEnumerator()
|
|
{ // TODO: a custom impl that is less garbage
|
|
yield return first;
|
|
foreach (var v in rest) yield return v;
|
|
}
|
|
|
|
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
|
|
}
|
|
|
|
/// <summary>
|
|
/// Adds a value to the end of the sequence.
|
|
/// </summary>
|
|
/// <typeparam name="T">the type of the elements of <paramref name="seq"/></typeparam>
|
|
/// <param name="seq">a sequence of values</param>
|
|
/// <param name="app">the value to append to <paramref name="seq"/></param>
|
|
/// <returns>a new sequence ending with <paramref name="app"/></returns>
|
|
public static IEnumerable<T> Append<T>(this IEnumerable<T> seq, T app)
|
|
=> new AppendEnumerable<T>(seq, app);
|
|
|
|
private sealed class AppendEnumerable<T> : IEnumerable<T>
|
|
{
|
|
private readonly IEnumerable<T> rest;
|
|
private readonly T last;
|
|
|
|
public AppendEnumerable(IEnumerable<T> rest, T last)
|
|
{
|
|
this.rest = rest;
|
|
this.last = last;
|
|
}
|
|
|
|
public IEnumerator<T> GetEnumerator()
|
|
{ // TODO: a custom impl that is less garbage
|
|
foreach (var v in rest) yield return v;
|
|
yield return last;
|
|
}
|
|
|
|
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
|
|
}
|
|
|
|
/// <summary>
|
|
/// LINQ extension method that filters <see langword="null"/> elements out of an enumeration.
|
|
/// </summary>
|
|
/// <typeparam name="T">the type of the enumeration</typeparam>
|
|
/// <param name="self">the enumeration to filter</param>
|
|
/// <returns>a filtered enumerable</returns>
|
|
public static IEnumerable<T> NonNull<T>(this IEnumerable<T> self) where T : class
|
|
=> self.Where(o => o != null);
|
|
|
|
/// <summary>
|
|
/// LINQ extension method that filters <see langword="null"/> elements out of an enumeration based on a converter.
|
|
/// </summary>
|
|
/// <typeparam name="T">the type of the enumeration</typeparam>
|
|
/// <typeparam name="U">the type to compare to null</typeparam>
|
|
/// <param name="self">the enumeration to filter</param>
|
|
/// <param name="pred">the predicate to select for filtering</param>
|
|
/// <returns>a filtered enumerable</returns>
|
|
public static IEnumerable<T> NonNull<T, U>(this IEnumerable<T> self, Func<T, U> pred) where U : class
|
|
=> self.Where(o => pred(o) != null);
|
|
|
|
/// <summary>
|
|
/// LINQ extension method that filters <see langword="null"/> elements from an enumeration of nullable types.
|
|
/// </summary>
|
|
/// <typeparam name="T">the underlying type of the nullable enumeration</typeparam>
|
|
/// <param name="self">the enumeration to filter</param>
|
|
/// <returns>a filtered enumerable</returns>
|
|
public static IEnumerable<T> NonNull<T>(this IEnumerable<T?> self) where T : struct
|
|
=> self.Where(o => o != null).Select(o => o.Value);
|
|
|
|
}
|
|
}
|