Strings\countSubString()

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reducer returns Closure pure

(string, int, int?) → (string → int)

At a glance — Bind a substring and optional search window; the returned Closure counts occurrences. Wraps substr_count().

Allows you to create a function which can be used to count the occurrence of a substring in a string. Allowing for the setting of an optional offset and limit. These can either be used as part of a Higher Order Function such as array_map() or as part of a compiled/pipe function.

/**
  * @param string $needle The substring to find
  * @param int $offset Place to start, defaults to 0 (start)
  * @param int|null $length Max length after offset to search.
  * @return Closure(string):int
  */
 Strings\countSubString(string $needle, int $offset = 0, ?int $length = null): Closure

Returned Closure

When Strings\countSubString() is called, it returns the following Closure which can be used like a regular function.

/**
  * @param string $haystack 
  * @return int
  * @psalm-pure
  */ 
$function(string $haystack): int

Examples

Partial Application

This can be used to create a simple closure which can be used as a regular function.

// Create a closure which will get all instances of IT in a string.
$countIt = Strings\countSubString('it'); 

// Create a closure which get all instance of IT after the first 3 letters in a string.
$countItAfter3 = Strings\countSubString('it', 3);

// Create a closure which get all instance of IT after the first 10 letters in a string, but only search the first 100 letters.
$countItBetween10_100 = Strings\countSubString('it', 10, 100);

// Called as a function.
echo countIt('This is a string, with it in it'); // 2
echo countItAfter3('It has it inside it'); // 2

// Used in a higher order function.
$array = array_map( $countIt, ['This is a string, with it in it', 'It has it inside it']);
print_r($array); // [2,3]

Curried

This can be called inline using currying.

echo Strings\countSubString('it')('It has it inside it'); // 3
echo Strings\countSubString('it', 3)('It has it inside it'); // 2

Inlined with Higher Order Function

If you are not planning on reusing the Closure created, you can just call it inline with a higher order function as its callable.

$array = array_map( 
  Strings\countSubString('it'), 
  ['This is a string, with it in it', 'It has it inside it']
);
print_r($array); // [2,3]

Details

Group: Strings
Subgroup: String analysis
Core Functions: substr_count()
Since: 0.1.0
Source: