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    <h3>Editing: BinaryOperator.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php declare(strict_types=1);
/*
 * This file is part of PHPUnit.
 *
 * (c) Sebastian Bergmann &lt;sebastian@phpunit.de&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */
namespace PHPUnit\Framework\Constraint;

use function array_map;
use function array_values;
use function count;

/**
 * @no-named-arguments Parameter names are not covered by the backward compatibility promise for PHPUnit
 */
abstract class BinaryOperator extends Operator
{
    /**
     * @var Constraint[]
     */
    private $constraints = [];

    public static function fromConstraints(Constraint ...$constraints): self
    {
        $constraint = new static;

        $constraint-&gt;constraints = $constraints;

        return $constraint;
    }

    /**
     * @param mixed[] $constraints
     */
    public function setConstraints(array $constraints): void
    {
        $this-&gt;constraints = array_map(function ($constraint): Constraint
        {
            return $this-&gt;checkConstraint($constraint);
        }, array_values($constraints));
    }

    /**
     * Returns the number of operands (constraints).
     */
    final public function arity(): int
    {
        return count($this-&gt;constraints);
    }

    /**
     * Returns a string representation of the constraint.
     */
    public function toString(): string
    {
        $reduced = $this-&gt;reduce();

        if ($reduced !== $this) {
            return $reduced-&gt;toString();
        }

        $text = '';

        foreach ($this-&gt;constraints as $key =&gt; $constraint) {
            $constraint = $constraint-&gt;reduce();

            $text .= $this-&gt;constraintToString($constraint, $key);
        }

        return $text;
    }

    /**
     * Counts the number of constraint elements.
     */
    public function count(): int
    {
        $count = 0;

        foreach ($this-&gt;constraints as $constraint) {
            $count += count($constraint);
        }

        return $count;
    }

    /**
     * Returns the nested constraints.
     */
    final protected function constraints(): array
    {
        return $this-&gt;constraints;
    }

    /**
     * Returns true if the $constraint needs to be wrapped with braces.
     */
    final protected function constraintNeedsParentheses(Constraint $constraint): bool
    {
        return $this-&gt;arity() &gt; 1 &amp;&amp; parent::constraintNeedsParentheses($constraint);
    }

    /**
     * Reduces the sub-expression starting at $this by skipping degenerate
     * sub-expression and returns first descendant constraint that starts
     * a non-reducible sub-expression.
     *
     * See Constraint::reduce() for more.
     */
    protected function reduce(): Constraint
    {
        if ($this-&gt;arity() === 1 &amp;&amp; $this-&gt;constraints[0] instanceof Operator) {
            return $this-&gt;constraints[0]-&gt;reduce();
        }

        return parent::reduce();
    }

    /**
     * Returns string representation of given operand in context of this operator.
     *
     * @param Constraint $constraint operand constraint
     * @param int        $position   position of $constraint in this expression
     */
    private function constraintToString(Constraint $constraint, int $position): string
    {
        $prefix = '';

        if ($position &gt; 0) {
            $prefix = (' ' . $this-&gt;operator() . ' ');
        }

        if ($this-&gt;constraintNeedsParentheses($constraint)) {
            return $prefix . '( ' . $constraint-&gt;toString() . ' )';
        }

        $string = $constraint-&gt;toStringInContext($this, $position);

        if ($string === '') {
            $string = $constraint-&gt;toString();
        }

        return $prefix . $string;
    }
}
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