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Add missing String.count/2 clause for empty pattern list #15342

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josevalim merged 2 commits into from
May 6, 2026
+11 −1
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Add missing String.count/2 clause for empty pattern list #15342

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eaf8989
Add missing String.count/2 clause for empty pattern list
lukaszsamson May 5, 2026
b255fc0
Clarify String.count pattern parameter in docs
josevalim May 6, 2026
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12 changes: 11 additions & 1 deletion lib/elixir/lib/string.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -745,7 +745,15 @@ defmodule String do
iex> String.count("hello world", "")
12

The `pattern` can also be a compiled pattern:
The `pattern` can also be a list:

iex> String.count("hello world", ["e", "o"])
3

iex> String.count("hello world", [])
0

Or a compiled pattern:

iex> pattern = :binary.compile_pattern([" ", "!"])
iex> String.count("foo bar baz!!", pattern)
Expand All @@ -756,6 +764,8 @@ defmodule String do
@doc since: "1.19.0"
def count(string, <<>>), do: length(string) + 1

def count(_string, []), do: 0

def count(string, pattern) when is_struct(pattern, Regex) do
Kernel.length(Regex.scan(pattern, string, return: :index))
end
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