fix Collections::reduce and Collections::reduceRight behaviour

[MamdouhAhmed]

Hello, and thanks for contributing to php-lodash

Description

The changes I made to reduce and reduceRight makes them both behave like their JS counterparts that they were modeled after, the change is potentially breaking for any code that relied heavily on, or just worked with, the existing implementation.

In the documentation for Array.prototype.reduce and Array.prototype.reduceRight, it is mentioned that in case of calling any of those functions without including an initial value, the function uses the first element of the array to be processed as its initial value and starts iterating from the next element. That way it doesn't double-process any of the values of the array.

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

Added new cases to the existing unit test to confirm that the changes have the intended effect. The snippet below shows concisely the effect of the changes.

$sum = __::reduce([2], function ($a, $b){return $a+$b;}); //before -> 4 -- processed the first element twice, after --> 2 
$sum = __::reduce([2], function ($a, $b){return $a+$b;}, 0); // before and after -> 2 -- an initial value was provided

Test Configuration:

• PHP Version: >=7.0

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[codecov-io]

Codecov Report

Merging #13 into master will not change coverage.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master      #13   +/-   ##
=========================================
  Coverage     98.51%   98.51%           
  Complexity      224      224           
=========================================
  Files             8        8           
  Lines           538      538           
=========================================
  Hits            530      530           
  Misses            8        8

Impacted Files	Coverage Δ	Complexity Δ
src/Traits/Collections.php	98.75% <100%> (ø)	119 <0> (ø)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 393a5a9...6c65d3b. Read the comment docs.

[meabed]

Thank you @MamdouhAhmed 👍