String Extensions

IndexOf

The classical IndexOf methods provide a special form of error handling by returning -1 when nothing is found. This is very cumbersome and a potential footgun, since you're not forced to check the return value.

Funcky offers extension methods on string for each overload of IndexOf, IndexOfAny, LastIndexOf, and LastIndexOfAny. The extension methods follow the simple convention of being suffixed with OrNone.

Option<string> ParseKey(string input)
    => input.IndexOfOrNone('[')
         .Select(startIndex => ParseKeyWithMultipleParts(input, startIndex))
         .GetOrElse(() => ParseRegularKey(input));

Example usage of IndexOfOrNone

Chunk and SlidingWindow

The sequence operations Chunk and SlidingWindow exist on string too, producing strings instead of lists of characters:

IEnumerable<string> Chunk(this string source, int size)
IEnumerable<string> SlidingWindow(this string source, int width)

"abcdefg".Chunk(3);          // ["abc", "def", "g"]
"abcde".SlidingWindow(3);    // ["abc", "bcd", "cde"]

The rules are the same as for sequences: the last chunk may be shorter, only full windows are produced, and a size or width of zero or less throws an ArgumentOutOfRangeException.

SplitLazy

string.Split allocates an array with all parts up front. SplitLazy produces the same parts one at a time, which matters when the string is large and you only need the first few parts, or when the parts are consumed by a streaming pipeline anyway.

IEnumerable<string> SplitLazy(this string text, char separator)
IEnumerable<string> SplitLazy(this string text, params char[] separators)
IEnumerable<string> SplitLazy(this string text, string separator)
IEnumerable<string> SplitLazy(this string text, params string[] separators)

var firstField = line.SplitLazy(',').FirstOrNone();

SplitLines

Splits text into lines, treating \n, \r and \r\n each as a line break, lazily.

IEnumerable<string> SplitLines(this string text)

A trailing line break does not produce an empty last line, and the empty string has no lines.

"first\r\nsecond\nthird\n".SplitLines();   // ["first", "second", "third"]