Counting char occurrences: retarget net10.0, fix IndexOf undercount, Regex.Count - #2218
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…Regex.Count
CountCharsUsingIndex skipped the character after each match, so adjacent
occurrences were counted as one ("aab" returned 1, "aaaa" returned 2).
Removed the extra increment and added a regression test for adjacent
occurrences, which the existing suite could not fail on.
Also:
- both projects retargeted from net6.0 to net10.0
- CommunityToolkit.HighPerformance removed; MemoryExtensions.Count() supplies
the same call from System since .NET 8
- CountCharsUsingRegex uses Regex.Count() instead of building a Regex per call
- new CountSubstringsAndFrequencies class with four tests, covering counting a
substring (overlapping and non-overlapping) and counting every character
- Program.cs lifted to top-level statements
- BenchmarkDotNet 0.15.8, Microsoft.NET.Test.Sdk 18.10.1, xunit 2.9.3,
xunit.runner.visualstudio 4.0.0, coverlet.collector 10.0.1
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Counting Occurrences of a Char Within a String: sample retargeted to .NET 10, with one real bug fix.
CountCharsUsingIndex()skipped the character immediately after each match, so two adjacent occurrences were counted as one: counting'a'in"aab"returned 1 and in"aaaa"returned 2. Every existing test used"Mary Had A Little Lamb", whose twoLs are seven characters apart, so the suite could never fail on it. The extra increment is removed and a regression test for adjacent occurrences is added.Also in this PR:
net6.0tonet10.0.CommunityToolkit.HighPerformanceremoved.MemoryExtensions.Count()has supplied the sameReadOnlySpan<T>extension fromSystemsince .NET 8, andCountCharsUsingSpanCount's body is unchanged.CountCharsUsingRegex()uses the staticRegex.Count()(.NET 7 and up) instead of constructing aRegexper call.Regex.Escape()is kept.CountSubstringsAndFrequenciesclass, not a benchmark class, holding the substring pair (non-overlapping spanCount()and an overlappingIndexOfloop) and the frequency-map pair (GroupBy().ToDictionary()and aforeachwithGetValueOrDefault()), with four tests.Program.cslifted to top-level statements.Build and tests on SDK 10.0.302 / runtime 10.0.10: 0 warnings, 0 errors, 16 of 16 passing.