On the margin of a problem solution

zoli.php

<?php

use Ds\Set;
use stdClass;

class Zoli
{

    protected array $range;
    protected const RANGE_MIN = 0;
    protected const RANGE_MAX = 5;
    protected const RANGE_STEP = 0.5;

    protected $a, $b, $c, $d = null;

    protected $crossOp, $cellOp;

    public function __construct(protected Set $set = new Set) {
        
        $this->range = range(
            self::RANGE_MIN, 
            self::RANGE_MAX, 
            self::RANGE_STEP
        );

        $this->crossOp = ($this->add(...));
        $this->cellOp = ($this->multiply(...));

    }

    protected function resetVariables(): void {
        $this->a =
        $this->b =
        $this->c =
        $this->d = null;
    }

    protected function extractGuess(array $guess): array {
        return [
            $this->a ?? $guess[0],
            $this->b ?? $guess[1],
            $this->c ?? $guess[2],
            $this->d ?? $guess[3],
        ];
    }

    protected function multiply(...$numbers): int|float {
        return array_reduce($numbers, 
            fn($accumulator, $number) => $accumulator * $number
        , 1);
    }

    protected function subtract(...$numbers): int|float {
        return array_reduce($numbers, 
            fn($accumulator, $number) => $accumulator - $number
        , 0);
    }

    protected function add(...$numbers): int|float {
        return array_reduce($numbers, 
            fn($accumulator, $number) => $accumulator + $number
        , 0);
    }

    protected function getSymbols(array $pairs): stdClass {
        return array_reduce($pairs, function($obj, $sub_array) {
            foreach ($sub_array as $sub_obj) {
                foreach ($sub_obj as $key => $value) {
                    if (!property_exists($obj, $key)) {
                        $obj->{$key} = $value;
                    }
                }
            }
            return $obj;
        }, new stdClass());
    }

    protected function fixVariables(stdClass $symbols):void {
        foreach($symbols as $symbol => $value) {
            $this->{$symbol} = $value;
        }
    }

    protected function eq(int $expectedResult, array $pairs): bool {

        $result = ($this->crossOp)(...array_map(function($cell) {
            return ($this->cellOp)(...array_map(fn($symbol) => array_values($symbol)[0], $cell));
        }, $pairs));

        if ($result == $expectedResult) {
            $this->fixVariables($this->getSymbols($pairs));
            return true;
        }

        return false;

    }

    protected function createPair(array $symbols, array $values): array {
        return array_map(function ($symbol, $value) {
            return [$symbol => $value];
        }, $symbols, $values); 
    }

    public function validateSolution(array $guess) {

        list($a, $b, $c, $d) = $this->extractGuess($guess);

        yield $this->eq(40, [
            $this->createPair(['a', 'a'], [$a, $a]), $this->createPair(['c', 'c'], [$c, $c]),
            $this->createPair(['c', 'c'], [$c, $c]), $this->createPair(['a', 'a'], [$a, $a])
        ]);
        
        yield $this->eq(26, [
            $this->createPair(['a', 'a'], [$a, $a]), $this->createPair(['a', 'a'], [$a, $a]),
            $this->createPair(['d', 'd'], [$d, $d]), $this->createPair(['d', 'd'], [$d, $d])
        ]);

        yield $this->eq(50, [
            $this->createPair(['c', 'c'], [$c, $c]), $this->createPair(['c', 'c'], [$c, $c]),
            $this->createPair(['d', 'd'], [$d, $d]), $this->createPair(['d', 'd'], [$d, $d])
        ]);

        yield $this->eq(14, [
            $this->createPair(['a', 'a'], [$a, $a]), $this->createPair(['b', 'c'], [$b, $c]),
            $this->createPair(['a', 'a'], [$a, $a]), $this->createPair(['a', 'b'], [$a, $b])
        ]);
        
        yield $this->eq(24, [
            $this->createPair(['b', 'c'], [$b, $c]), $this->createPair(['d', 'b'], [$d, $b]),
            $this->createPair(['c', 'c'], [$c, $c]), $this->createPair(['b', 'b'], [$b, $b])
        ]);
        
        yield $this->eq(31, [
            $this->createPair(['c', 'c'], [$c, $c]), $this->createPair(['d', 'b'], [$d, $b]),
            $this->createPair(['a', 'a'], [$a, $a]), $this->createPair(['c', 'a'], [$c, $a])
        ]);

        yield $this->eq(26, [
            $this->createPair(['a', 'a'], [$a, $a]), $this->createPair(['b', 'b'], [$b, $b]), 
            $this->createPair(['d', 'd'], [$d, $d]), $this->createPair(['c', 'd'], [$c, $d])
        ]);

        yield $this->eq(31, [
            $this->createPair(['a', 'b'], [$a, $b]), $this->createPair(['c', 'a'], [$c, $a]),
            $this->createPair(['d', 'd'], [$d, $d]), $this->createPair(['c', 'd'], [$c, $d])
        ]);

    }

    public function getRandomElement() {
        return $this->range[array_rand($this->range)];
    }

    public function generateElements(): array {
        return array_map(fn() => $this->getRandomElement(), range(1, 4));
    }

    public function checkIfGuessExists($guess): bool {
        return $this->set->contains($guess);
    }

    public function generateGuess(): array {

        $guess = $this->generateElements();
        while ($this->checkIfGuessExists($guess) || count(array_unique($guess)) !== 4)
            $guess = $this->generateElements();
        return $guess;

    }

    public function evaluateSolution(array $guess): bool {

        return array_reduce([...$this->validateSolution($guess)],
            fn ($validGuess, $eq) => $validGuess && $eq
        , true);

    }

    public function printSolution(array $solution): void {
        echo sprintf("We have found a solution: a = %.1f, b = %.1f, c = %.1f, d = %.1f", ...$solution);
    }
    public function runSequence(int $length = 5000): bool {

        $this->set->clear();

        for ($j = 0; $j < $length; $j++) {

            $guess = $this->generateGuess();

            if ($this->evaluateSolution($guess)) {
                $this->printSolution($this->extractGuess($guess));
                return true;
            } else {
                $this->set->add($guess);
            }

        }

        sleep(15);
        $this->resetVariables();
        return false;

    }

}