# Ds\Sequence::reduce

(PECL ds >= 1.0.0)

Ds\Sequence::reduceReduces the sequence to a single value using a callback function.

### 설명

abstract public mixed Ds\Sequence::reduce ( callable \$callback [, mixed \$initial ] )

Reduces the sequence to a single value using a callback function.

### 인수

callback
mixed callback ( mixed \$carry , mixed \$value )
carry

The return value of the previous callback, or initial if it's the first iteration.

value

The value of the current iteration.

initial

The initial value of the carry value. Can be NULL.

### 반환값

The return value of the final callback.

### 예제

Example #1 Ds\Sequence::reduce() with initial value example

<?php
\$sequence
= new \Ds\Vector([123]);

\$callback = function(\$carry\$value) {
return
\$carry \$value;
};

var_dump(\$sequence->reduce(\$callback5));

// Iterations:
//
// \$carry = \$initial = 5
//
// \$carry = \$carry * 1 =  5
// \$carry = \$carry * 2 = 10
// \$carry = \$carry * 3 = 30
?>

위 예제의 출력 예시:

int(30)

Example #2 Ds\Sequence::reduce() without an initial value example

<?php
\$sequence
= new \Ds\Vector([123]);

var_dump(\$sequence->reduce(function(\$carry\$value) {
return
\$carry \$value 5;
}));

// Iterations:
//
// \$carry = \$initial = null
//
// \$carry = \$carry + 1 + 5 =  6
// \$carry = \$carry + 2 + 5 = 13
// \$carry = \$carry + 3 + 5 = 21
?>

위 예제의 출력 예시:

int(21)