predicate による文字列分割を行う `String` 拡張メソッド。

StringSplitExtensions.cs

#nullable enable

using System;
using System.Collections.Generic;

namespace Commons {

    public delegate bool StringSplitPredicate(ref int index);

    public static class StringExtensions {

        public static IEnumerable<string> Split(this string value, StringSplitPredicate predicate) {
            if (value is null) { throw new ArgumentNullException(nameof(value)); }
            if (predicate is null) { throw new ArgumentNullException(nameof(predicate)); }

            int prevIndex = 0;
            for (int i = 0; i < value.Length; i++) {
                int currentIndex = i;
                if (predicate(ref i)) {
                    yield return value.Substring(prevIndex, currentIndex - prevIndex);
                    prevIndex = i;
                }
            }

            yield return value.Substring(prevIndex);
        }
    }
}

#nullable restore