rambkk/PHP-array_reduce,findIndex,findIndexes.php

	<?php
	/*
	* PHP array_reduce_key (v0.11) - array_reduce with additional parameters
	* array_reduce with key,
	* (javascript like reduce method)
	* (if initial value of carry is not specified, null is used)
	*
	* PHP array_reduce_JS (v0.12) - array_reduce with additional parameters
	* (javascript like reduce method)
	* if initial value of carry is not specified, first item of input ARRAY is used, and CALLBACK starts on the second item
	*
	* PHP findIndex (v0.1) - get index of first array item which passes callback
	* (javascript like findIndex)
	*
	* PHP findIndexes (v0.1) - get index list of items which passes callback on array
	*
	* (c) Ram Narula You can use this information, kindly do give credit: github rambkk - Ram Narula - pluslab.net
	* Please drop a line to say hello and let me know what kind of project you are working on :-)
	* rambkk - pluslab.net - looking for impossible projects
	*/

	$intro=<<<'_____'

	* Requirement:
	* PHP 5 >= 5.3.0, PHP 7, PHP 8 (without using Arrow function)
	* PHP 7 >= 7.4, PHP 8 (optional for using Arrow function)
	* (Tested on php 7.4.3)
	*
	* Syntax:
	*
	* ---------------
	* array_reduce_key ( ARRAY, CALLBACK($c,$v,$i,$a), [optional: initial value of $c] )
	* ---------------
	* This works the same way as general PHP array_reduce function with
	* the addition of additional optional parameters to the CALLBACK
	*
	* Run CALLBACK on each item of ARRAY and put the result as $c for the next CALLBACK
	* Result from CALLBACK on last item will be returned
	* The default initial value of $c is null
	*
	* NOTE: This can work as a drop-in replacement for array_reduce function
	* NOTE: For more information look up PHP array_reduce function
	* NOTE: array_reduce_key needs more processing resources than the built-in array_reduce
	*
	* ---------------
	* array_reduce_JS ( ARRAY, CALLBACK($c,$v,$i,$a), [optional: initial value of $c] )
	* ---------------
	* This works the same way as general PHP array_reduce function with
	* the addition of additional optional parameters to the CALLBACK
	*
	* Run CALLBACK on each item of ARRAY and put the result as $c for the next CALLBACK
	* Result from CALLBACK on last item will be returned
	* The default initial value of $c is the first item of the ARRAY and the CALLBACK starts
	* on the second item as $v
	*
	* NOTE: This can work as a drop-in replacement for array_reduce function
	* NOTE: For more information look up PHP array_reduce function
	* NOTE: array_reduce_JS needs more processing resources than the built-in array_reduce
	*
	* ---------
	* findIndex ( ARRAY, CALLBACK($v,$i,$a) )
	* ---------
	* Get the first key/index of the array from a truthy/success from CALLBACK
	* otherwise returns null
	* NOTE: javascript findIndex returns -1 for failing
	*
	* -----------
	* findIndexes ( ARRAY, CALLBACK($v,$i,$a) )
	* -----------
	* Get an array of index of all items for each truthy/success from CALLBACK
	* otherwise returns an empty array
	*
	* -------------------
	* CALLBACK parameters
	* -------------------
	* $c (ONLY for array_reduce_JS/array_reduce_key) initial value or return value from the last CALLBACK
	* $v value of current item
	* $i index of current item (optional)
	* $a current array (optional)
	*
	*
	* ---------------------
	* Using these functions
	* ---------------------
	* Anonymous function (PHP 5 >= 5.3.0, PHP 7, PHP 8)
	* Arrow function (PHP 7 >= 7.4, PHP 8) (optional)
	*
	*
	* Author: Ram Narula <github: rambkk> OR <www.pluslab.net>
	*
	*
	* How to use?
	* Put the initial declaration
	*
	*
	* Why?
	* It is a fun challenge to create very compact codes.
	*
	*
	_____;
	/* ----------- */
	/* Declaration */
	/* ----------- */


	function array_reduce_key($a,$f,$c=null){foreach($a as $k=>$v)$c=$f($c,$v,$k,$a);return $c;}
	function findIndex($a,$f){foreach($a as $k=>$v)if($f($v,$k,$a))return $k;}
	function findIndexes($a,$f){$r=[];foreach($a as $k=>$v)if($f($v,$k,$a))$r[]=$k;return $r;}
	function array_reduce_JS($a,$f,...$arg){ $arg?$c=$arg[0]:$c=$a[key($a)];foreach($arg?$a:array_slice($a,1,null,true) as $k=>$v)$c=$f($c,$v,$k,$a);return $c; }

	//Anonymous functions as some might prefer
	$array_reduce_key=function($a,$f,$c=null){foreach($a as $k=>$v)$c=$f($c,$v,$k,$a);return $c;};
	$array_reduce_JS=function($a,$f,...$arg){ $arg?$c=$arg[0]:$c=$a[key($a)];foreach($arg?$a:array_slice($a,1,null,true) as $k=>$v)$c=$f($c,$v,$k,$a);return $c; };
	$findIndex=function($a,$f){foreach($a as $k=>$v)if($f($v,$k,$a))return $k;};
	$findIndexes=function($a,$f){$r=[];foreach($a as $k=>$v)if($f($v,$k,$a))$r[]=$k;return $r;};


	/* Examples: */

	$list=[1,2,3,4,5];
	$initial=10000;

	$sumOdd=array_reduce_key($list,function($c,$v){ if($v % 2 == 1) { return $v+$c; } else { return $c; } },$initial);
	echo "Sum odd with initial: $sumOdd\n";


	//with ternary operator instead of if
	$sumEven=array_reduce_key($list,function($c,$v){return ($v % 2 == 0)?$v+$c:$c; });
	echo "Sum even: $sumEven\n";


	$sumEvenIndex=array_reduce_key($list,function($c,$v,$i,$a){return ($i % 2 === 0)?$v+$c:$c; });
	echo "Sum of items with even index numbers (index starts with 0): $sumEvenIndex\n";

	array_reduce_key($list,function($c,$v,$i,$a){echo "($c ... $v)"; });
	// ( ... 1)( ... 2)( ... 3)( ... 4)( ... 5)

	array_reduce_JS($list,function($c,$v,$i,$a){echo "$c ... $v"; });
	// (1 ... 2)( ... 3)( ... 4)( ... 5)
	// Note the difference:
	// without initial value of $c, the default initial value is the first item of input ARRAY
	// and the function runs with second item of ARRAY for $v and $i



	/* Additional examples */

	$List=[
	["plant"=>"lotus","new"=>true, "comment"=>"morning"],
	["plant"=>"clove","new"=>true, "comment"=>"aroma"],
	["plant"=>"juniper","new"=>true, "comment"=>"aromatic"],
	["plant"=>"agarwood","new"=>true, "comment"=>"hard to find"],
	["plant"=>"sandalwood","new"=>true, "comment"=>"coming"],
	["plant"=>"sandalwood","new"=>false, "comment"=>"not sure"],
	["plant"=>"agarwood","new"=>true, "comment"=>"ok"],
	["plant"=>"juniper","new"=>false, "comment"=>"not sure"]
	];
	$List[-1]=['plant'=>'sandalwood',"new"=>false];
	$List[-108]=['plant'=>'udumbara',"new"=>false];


	$RList=[
	["plant"=>"sandalwood","new"=>false],
	["plant"=>"juniper","new"=>true]
	];


	//eg. get array of indexes where plant is 'udumbara' OR 'sandalwood'
	echo "Arrow function: ";
	$r=findIndexes($List,fn($w,$i,$a) => $w['plant']=='udumbara' \|\| $w['plant']=='sandalwood'); print_r($r); // [4,5,-1,-108]

	echo "Inline function: ";
	$r=findIndex($List,function($w,$i,$a){ return $w['plant']=='juniper' && $w['new']===false; }); echo "$r\n"; // 7

	echo "Anonymous function: ";
	$func=function($w,$i) { return $w['plant']=='juniper'; };
	$r=findIndex($List,$func); echo "$r\n"; // 2

	echo "Function (using quotes to point to function name without parameter): ";
	function func($w,$i) { return $w['plant']=='juniper'; }
	$r=findIndex($List,'func'); echo "$r\n"; // 2

	echo "Function nested with parameter: ";
	$findThis='juniper';
	function funcOuter($name) { return function($w) use ($name) {
	return $w['plant']==$name;
	};
	}
	$r=findIndex($List,funcOuter($findThis)); echo "$r\n"; // 2



	//Slightly more complex examples, with using array_filter
	//
	//Remove $List entries with duplicate pairs of 'plant' AND 'new'
	//
	//$v current item of array_filter
	//$k being index from array_filter
	//... can pass these and other parameters as needed
	//
	//$w,$i,$a is from the findIndex CALLBACK on the array
	//
	//
	echo "Inline arrow function using List twice: ";
	$r=array_filter($List,fn($v,$k) => findIndex($List,fn($w) => $w['plant']==$v['plant'] && $w['new']===$v['new']) == $k,ARRAY_FILTER_USE_BOTH);
	print_r($r); echo "\n";


	echo "Inline function: ";
	$r=array_filter($List,fn($v,$k) => findIndex($List,function($w,$i,$a) use ($v) {return $w['plant']==$v['plant'] && $w['new']===$v['new'];}) == $k,ARRAY_FILTER_USE_BOTH);
	print_r($r);




	//
	//Note: $func2(...) <--- use brackets when calling
	// same results from these
	//
	echo "Arrow function nesting: ";
	$func2 = fn($v,$k) => fn($w,$i,$a) => $w['plant']==$v['plant'] && $w['new']===$v['new'];

	echo "Anonymous function and arrow function: ";
	$func2 = function($v,$k) { return fn($w,$i,$a) => $w['plant']==$v['plant'] && $w['new']===$v['new']; }; // <--- semi-colon required

	echo "Anonymous function nesting note the semi-colon ';' requirements: ";
	$func2 = function($v,$k) {
	return function($w,$i,$a) use ($v,$k) {
	return $w['plant']==$v['plant'] && $w['new']===$v['new'];
	}; // <--- semi-colon required
	}; // <--- semi-colon required
	$r=array_filter($List,fn($v,$k) => findIndex($List,$func2($v,$k)) == $k,ARRAY_FILTER_USE_BOTH);
	print_r($r);


	echo "Function nesting: ";
	function func2($v,$k) {
	return function($w,$i,$a) use ($v,$k) {
	return $w['plant']==$v['plant'] && $w['new']===$v['new'];
	}; // <--- semi-colon required
	}
	$r=array_filter($List,fn($v,$k) => findIndex($List,func2($v,$k)) == $k,ARRAY_FILTER_USE_BOTH);
	print_r($r);


	echo "Function inline nesting: ";
	$r=array_filter($List, function($v,$k) use ($List) {
	return findIndex($List, function($w,$i,$a) use ($v,$k) {
	return $w['plant']==$v['plant'] && $w['new']===$v['new'];
	} )==$k;
	} ,ARRAY_FILTER_USE_BOTH);
	print_r($r);
	/* Array (
	[0] => Array ( [plant] => lotus [new] => 1 [comment] => morning )
	[1] => Array ( [plant] => clove [new] => 1 [comment] => aroma )
	[2] => Array ( [plant] => juniper [new] => 1 [comment] => aromatic )
	[3] => Array ( [plant] => agarwood [new] => 1 [comment] => hard to find )
	[4] => Array ( [plant] => sandalwood [new] => 1 [comment] => coming )
	[5] => Array ( [plant] => sandalwood [new] => [comment] => not sure )
	[7] => Array ( [plant] => juniper [new] => [comment] => not sure )
	[-108] => Array ( [plant] => udumbara [new] => )
	) */


	//Remove entries $List with matching pairs of (plant AND new) in $RList
	//
	//NOTE:
	//must use strict type comparison ('===') with null (not found)
	//or use is_null function
	//
	echo "Inline arrow:";
	$r=array_filter($List,fn($v) => findIndex($RList,fn($w) => $w['plant']==$v['plant'] && $w['new']===$v['new'])===null );
	print_r($r);
	/* Array (
	[0] => Array ( [plant] => lotus [new] => 1 [comment] => morning )
	[1] => Array ( [plant] => clove [new] => 1 [comment] => aroma )
	[3] => Array ( [plant] => agarwood [new] => 1 [comment] => hard to find )
	[4] => Array ( [plant] => sandalwood [new] => 1 [comment] => coming )
	[6] => Array ( [plant] => agarwood [new] => 1 [comment] => ok )
	[7] => Array ( [plant] => juniper [new] => [comment] => not sure )
	[-108] => Array ( [plant] => udumbara [new] => )
	) */

	//
	//Example with negative key/index
	//
	echo "Inline arrow function (negative index): ";
	$r=findIndex($List,fn($w) => $w['plant']=='udumbara');
	var_dump($r);