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ihor/nspl
=========

Non-standard PHP library (NSPL) - functional primitives toolbox and more

1.3(7y ago)381368.5k↑70%16[4 PRs](https://github.com/ihor/Nspl/pulls)MITPHPPHP >=7.1.0

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Non-standard PHP library (NSPL)
===============================

[](#non-standard-php-library-nspl)

Non-standard PHP Library (NSPL) is a collection of modules that are meant to solve common day to day routine problems:

- [nspl\\f](#nsplf) - provides functions that act on other functions. Helps to write code in functional programming paradigm
- [nspl\\op](#nsplop) - provides functions that perform standard PHP operations and can be passed as callbacks to higher-order functions. Mimics Python's [operator](https://docs.python.org/2/library/operator.html) module
- [nspl\\a](#nspla) - provides missing array functions which also can be applied to traversable sequences
- [nspl\\a\\lazy](#nsplalazy) - provides lazy versions of functions from `\nspl\a`
- [nspl\\args](#nsplargs) - validates function arguments (will be moved into a separate package in version 2.0)
- [nspl\\ds](#nsplds) - provides non-standard data structures and methods to work with them
- [nspl\\rnd](#nsplrnd) - helps to pick random items from sequences of data

NSPL aims to make code compact and less verbose but still clear and readable. Look at the following example:

```
// get user ids
$userIds = map(propertyGetter('id'), $users);

// or sort them by age
$sortedByAge = sorted($users, methodCaller('getAge'));

// or check if they all are online
$online = all($users, methodCaller('isOnline'));

// or define new function as composition of the existing ones
$flatMap = compose(rpartial(flatten, 1), map);
```

In pure PHP it would look like this:

```
// get user ids
$userIds = array_map(function($user) { return $user->id; }, $users);

// sort them by age, note that the following code modifies the original users array
usort($users, function($user1, $user2) {
    return $user1->getAge() - $user2->getAge();
});

// check if they all are online
$online = true;
foreach ($users as $user) {
    if (!$user->isOnline()) {
        $online = false;
        break;
    }
}

// define new function as composition of the existing ones
$flatMap = function($function, $list) {
    // note the inconsistency in array_map and array_reduce parameters
    return array_reduce(array_map($function, $list), 'array_merge', []);
};
```

You can see more examples in the [library reference](#reference) below or [here](https://github.com/ihor/Nspl/blob/master/examples).

Installation
------------

[](#installation)

#### Using [composer](https://getcomposer.org)

[](#using-composer)

Define the following requirement in your composer.json file:

```
"require": {
    "ihor/nspl": "~1.3"
}

```

or execute the following in the command line:

```
composer require ihor/nspl

```

For the latest version which contains way more functionality require version `2.0.*-dev`

#### Manually

[](#manually)

Checkout [the code](https://github.com/ihor/Nspl) and include `autoload.php`:

```
include 'path/to/nspl/autoload.php';
```

Reference
=========

[](#reference)

This is documentation for the dev version `2.0.*-dev` which contains the latest changes. For the version `1.3` (latest stable version) documentation click [here](https://github.com/ihor/Nspl/tree/1.3).

Here I assume that described functions are imported with [use function](http://php.net/manual/en/language.namespaces.importing.php):

```
use function nspl\a\zip;
$pairs = zip([1, 2, 3], ['a', 'b', 'c']);
```

If your PHP version is less than 5.6 you should import parent namespace and use functions with the namespace prefix:

```
use nspl\a;
$pairs = a\zip([1, 2, 3], ['a', 'b', 'c']);
```

Table of contents
-----------------

[](#table-of-contents)

- [nspl\\f](#nsplf)
    - [id](#idvalue)
    - [apply](#applyfunction-array-args--)
    - [partial](#partialfunction-arg1)
    - [rpartial](#rpartialfunction-arg1)
    - [ppartial](#ppartialfunction-array-args)
    - [flipped](#flippedfunction)
    - [compose](#composef-g)
    - [pipe](#pipeinput-function1-function2)
    - [curried](#curriedfunction-withoptionalargs--false)
    - [uncurried](#uncurriedfunction)
    - [memoized](#memoizedfunction)
    - [throttled](#throttledfunction-wait)
    - [Callbacks](#callbacks)
- [nspl\\op](#nsplop)
    - [Callbacks](#callbacks-1)
    - [itemGetter](#itemgetterkey)
    - [propertyGetter](#propertygetterproperty)
    - [methodCaller](#methodcallermethod-array-args--array)
    - [instanceCreator](#instancecreatorclass)
- [nspl\\a](#nspla)
    - [all](#allsequence-predicate)
    - [any](#anysequence-predicate)
    - [map](#mapfunction-sequence)
    - [flatMap](#flatmapfunction-sequence)
    - [zip](#zipsequence1-sequence2)
    - [zipWith](#zipwithfunction-sequence1-sequence2)
    - [reduce](#reducefunction-sequence-initial--0)
    - [filter](#filterpredicate-sequence)
    - [filterNot](#filternotpredicate-sequence)
    - [take](#takesequence-n-step--1)
    - [takeKeys](#takekeyssequence-array-keys)
    - [takeWhile](#takewhilepredicate-sequence)
    - [first](#firstsequence)
    - [second](#secondsequence)
    - [drop](#dropsequence-n)
    - [dropKeys](#dropkeyssequence-array-keys)
    - [dropWhile](#dropwhilepredicate-sequence)
    - [last](#lastsequence)
    - [partition](#partitionpredicate-sequence)
    - [span](#spanpredicate-sequence)
    - [indexed](#indexedsequence-by-keeplast--true-transform--null)
    - [sorted](#sortedsequence-reversed--false-key--null-cmp--null)
    - [keySorted](#keysortedsequence-reversed--false)
    - [flatten](#flattensequence-depth--null)
    - [pairs](#pairssequence-valuekey--false)
    - [merge](#mergesequence1-sequence2)
    - [reorder](#reorderarray-list-from-to)
    - [value](#valuearray-key-default--null)
    - [values](#valuessequence)
    - [keys](#keyssequence)
    - [in](#initem-sequence)
    - [diff](#diffsequence1-sequence2)
    - [intersect](#intersectsequence1-sequence2)
    - [cartesianProduct](#cartesianproductsequences)
    - [isList](#islistvar)
    - [Chaining](#chaining)
    - [Callbacks](#callbacks-2)
- [nspl\\a\\lazy](#nsplalazy)
- [nspl\\args](#nsplargs)
    - [expects](#expectsconstraints-arg-atposition--null-otherwisethrow--invalidargumentexception)
    - [expectsAll](#expectsallconstraints-array-args-array-atpositions---otherwisethrow--invalidargumentexception)
    - [expectsOptional](#expectsoptionalconstraints-arg-atposition--null-otherwisethrow--invalidargumentexception)
    - [Predefined constraints](#predefined-constraints)
    - [Custom constraints](#custom-constraints)
- [nspl\\ds](#nsplds)
    - [DefaultArray](#defaultarray)
    - [Set](#set)
- [nspl\\rnd](#nsplrnd)
    - [randomString](#length)
    - [choice](#choicesequence)
    - [weightedChoice](#weightedchoiceweightpairs)
    - [sample](#samplepopulation-length-preservekeys--false)
- [nspl](#nspl)
    - [getType](#gettypevar)

nspl\\f
-------

[](#nsplf)

Provides functions that act on other functions. Helps to write code in the functional programming paradigm.

##### id($value)

[](#idvalue)

Identity function. Returns passed value.

```
assert(1 === id(1));
```

##### apply($function, array $args = \[\])

[](#applyfunction-array-args--)

Applies given function to arguments and returns the result

```
assert([1, 3, 5, 7, 9] === apply('range', [1, 10, 2]));
```

##### partial($function, $arg1)

[](#partialfunction-arg1)

Returns new partial function which will behave like `$function` with predefined *left* arguments passed to partial

```
$sum = function($a, $b) { return $a + $b; };
$inc = partial($sum, 1);
```

##### rpartial($function, $arg1)

[](#rpartialfunction-arg1)

Returns new partial function which will behave like `$function` with predefined *right* arguments passed to rpartial

```
$cube = rpartial('pow', 3);
```

##### ppartial($function, array $args)

[](#ppartialfunction-array-args)

Returns new partial function which will behave like `$function` with predefined *positional* arguments passed to ppartial

```
$oddNumbers = ppartial('range', array(0 => 1, 2 => 2));
```

##### flipped($function)

[](#flippedfunction)

Returns function which accepts arguments in the reversed order

##### compose($f, $g)

[](#composef-g)

Returns new function which applies each given function to the result of another from right to left `compose(f, g, h)` is the same as `f(g(h(x)))`

```
use const \nspl\a\flatten;
use const \nspl\a\map;
use function \nspl\f\compose;
use function \nspl\f\partial;
use function \nspl\f\rpartial;

$flatMap = compose(rpartial(flatten, 1), map);
assert(['hello', 'world', 'foo', 'bar'] === $flatMap(partial('explode', ' '), ['hello world', 'foo bar']));
```

##### pipe($input, $function1, $function2)

[](#pipeinput-function1-function2)

Passes `$input` to composition of functions (functions have to be in the reversed order)

```
use const \nspl\op\sum;
use const \nspl\a\filter;
use const \nspl\a\map;
use const \nspl\a\reduce;
use function \nspl\f\partial;

$isEven = function($x) { return $x % 2 === 0; };
$square = function($x) { return $x * $x; };

// sum of squares of all even numbers less than 20
$sum = pipe(
    range(1, 20),
    partial(filter, $isEven),
    partial(map, $square),
    partial(reduce, sum)
);
```

> **Tip**
>
> You can use [chaining](#chaining) to get rid of partials in sequence transformations:
>
> ```
> use function \nspl\a\with;
>
> $sum = with(range(1, 20))
>    ->filter($isEven)
>    ->map($square)
>    ->reduce(sum);
> ```

##### curried($function, $withOptionalArgs = false)

[](#curriedfunction-withoptionalargs--false)

Returns a [curried](https://en.wikipedia.org/wiki/Currying) version of the function. If you are going to curry a function which reads args with `func_get_args()` then pass the number of args as the 2nd argument.

If the second argument is true, then curry function with optional args otherwise curry it only with required args. Alternatively, you can pass the exact number of args you want to curry.

##### uncurried($function)

[](#uncurriedfunction)

Returns normal (uncurried) version of a [curried function](https://en.wikipedia.org/wiki/Currying)

##### memoized($function)

[](#memoizedfunction)

Returns memoized `$function` which returns the cached result when the same inputs occur again

```
$f = function($arg) {
    echo sprintf("Performing heavy calculations with '%s'\n", $arg);
    return $arg;
};

$memoized = memoized($f);
echo $memoized('Hello world!') . "\n";
echo $memoized('Hello world!') . "\n";
```

which outputs

```
Performing heavy calculations with 'Hello world!'
Hello world!
Hello world!

```

##### throttled($function, $wait)

[](#throttledfunction-wait)

Returns throttled version of the passed function, that, when invoked repeatedly, will only actually call the original function at most once per every wait milliseconds.

```
$f = function() {
    echo "Invoked\n";
};

$throttled = throttled($f, 10);

$startedAt = microtime(true);
do {
    $throttled();
} while((microtime(true) - $startedAt) * 1000 < 30); // 30ms
```

which outputs

```
Invoked
Invoked
Invoked

```

##### Callbacks

[](#callbacks)

`nspl\f` provides all its functions as callbacks in its constants which have the same names as the functions.

```
use const \nspl\a\map;
use const \nspl\a\filter;

$incListItems = partial(map, function($v) { return $v + 1; });
$filterNumbers = partial(filter, 'is_numeric');
```

Check more `\nspl\f` examples [here](https://github.com/ihor/Nspl/blob/master/examples/f.php).

nspl\\op
--------

[](#nsplop)

Class `nspl\op` provides functions that perform standard PHP operations and can be passed as callbacks to higher-order functions. Mimics Python's [operator](https://docs.python.org/2/library/operator.html) module. For example:

```
use const nspl\op\sum;
use function nspl\a\reduce;

assert(6 === reduce(sum, [1, 2, 3]));
```

##### Callbacks

[](#callbacks-1)

The module provides the following operations both as functions and callbacks. See an example below.

FunctionOperationsum+sub-mul\*div/mod%inc++dec--neg-band&amp;bxor^bor|bnot~lshift&lt;&lt;rshift&gt;&gt;lt&lt;le&lt;=eq==idnt===ne!=nidnt!==gt&gt;ge&gt;=and\_&amp;&amp;or\_||xor\_xornot!concat.instanceof\_instanceofint(int)bool(bool)float(float)str(string)array\_(array)object(object)##### itemGetter($key)

[](#itemgetterkey)

Returns a function that returns key value for a given array

```
use function nspl\op\itemGetter;
use function nspl\a\map;

assert([2, 5, 8] === map(itemGetter(1), [[1, 2, 3], [4, 5, 6], [7, 8, 9]]));
```

##### propertyGetter($property)

[](#propertygetterproperty)

Returns a function that returns property value for a given object

```
$userIds = map(propertyGetter('id'), $users);
```

##### methodCaller($method, array $args = array())

[](#methodcallermethod-array-args--array)

Returns a function that returns method result for a given object on predefined arguments

```
$userIds = map(methodCaller('getId'), $users);
```

##### instanceCreator($class)

[](#instancecreatorclass)

Returns a function that returns a new instance of a predefined class, passing its parameters to the constructor

```
$users = map(instanceCreator(User::class), $usersData);
```

Check more `\nspl\op` examples [here](https://github.com/ihor/Nspl/blob/master/examples/op.php).

nspl\\a
-------

[](#nspla)

Provides missing array functions which also can be applied to traversable sequences

##### all($sequence, $predicate)

[](#allsequence-predicate)

Returns true if all of the ````$sequence`items satisfy the predicate (or if the`$sequence``` is empty). If the predicate was not passed returns true if all of the ```$sequence``` items are true.

```
assert(true === all([true, true, true]));
```

##### any($sequence, $predicate)

[](#anysequence-predicate)

Returns true if any of the `$sequence` items satisfy the predicate. If the predicate was not passed returns true if any of the `$sequence` items are true.

```
assert(true === any([true, false, false]));
```

##### map($function, $sequence)

[](#mapfunction-sequence)

Applies function of one argument to each sequence item

```
assert(['A', 'B', 'C'] === map('strtoupper', ['a', 'b', 'c']));
```

##### flatMap($function, $sequence)

[](#flatmapfunction-sequence)

Applies function of one argument to each sequence item and flattens the result

```
$duplicate = function($v) { return [$v, $v]; }
assert(['hello', 'hello', 'world', 'world'] === flatMap($duplicate, ['hello', 'world']));
```

##### zip($sequence1, $sequence2)

[](#zipsequence1-sequence2)

Zips two or more sequences

```
assert([[1, 'a'], [2, 'b'], [3, 'c']] === zip([1, 2, 3], ['a', 'b', 'c']));
```

##### zipWith($function, $sequence1, $sequence2)

[](#zipwithfunction-sequence1-sequence2)

Generalises zip by zipping with the function given as the first argument, instead of an array-creating function

```
use const \nspl\op\sum;

assert([101, 1002, 10003] === zipWith(sum, [1, 2, 3], [100, 1000, 10000]));
```

##### reduce($function, $sequence, $initial = 0)

[](#reducefunction-sequence-initial--0)

Applies function of two arguments cumulatively to the sequence items, from left to right to reduce the sequence to a single value

```
assert(6 === reduce(function($a, $b) { return $a + $b; }, [1, 2, 3]));

// Which is the same as
use const \nspl\op\sum;
assert(6 === reduce(sum, [1, 2, 3]));
```

##### filter($predicate, $sequence)

[](#filterpredicate-sequence)

Returns sequence items that satisfy the predicate

```
assert([1, 2, 3] === filter('is_numeric', ['a', 1, 'b', 2, 'c', 3]));
```

##### filterNot($predicate, $sequence)

[](#filternotpredicate-sequence)

Returns sequence items that don't satisfy the predicate

```
assert(['a', 'b', 'c'] === filterNot('is_numeric', ['a', 1, 'b', 2, 'c', 3]));
```

##### take($sequence, $N, $step = 1)

[](#takesequence-n-step--1)

Returns the first N sequence items with the given step

```
assert([1, 3, 5] === take([1, 2, 3, 4, 5, 6, 7, 8, 9], 3, 2));
```

##### takeKeys($sequence, array $keys)

[](#takekeyssequence-array-keys)

Returns sequence containing only the given keys

```
assert(array('hello' => 1, 'world' => 2) === takeKeys(array('hello' => 1, 'world' => 2, 'foo' => 3), ['hello', 'world']));
```

##### takeWhile($predicate, $sequence)

[](#takewhilepredicate-sequence)

Returns the longest sequence prefix of all items which satisfy the predicate

```
assert([1, 2, 3] === takeWhile('is_numeric', [1, 2, 3, 'a', 'b', 'c', 4, 5, 6]));
```

##### first($sequence)

[](#firstsequence)

Returns the first sequence item

```
assert(1 === first([1, 2, 3, 4, 5, 6, 7, 8, 9]));
```

##### second($sequence)

[](#secondsequence)

Returns the second sequence item

```
assert(2 === second([1, 2, 3, 4, 5, 6, 7, 8, 9]));
```

##### drop($sequence, $N)

[](#dropsequence-n)

Drops the first N sequence items

```
assert([7, 8, 9] === drop([1, 2, 3, 4, 5, 6, 7, 8, 9], 6));
```

##### dropKeys($sequence, array $keys)

[](#dropkeyssequence-array-keys)

Returns array containing all keys except the given ones

```
assert(array('hello' => 1, 'world' => 2) === dropKeys(array('hello' => 1, 'world' => 2, 'foo' => 3), ['foo']));
```

##### dropWhile($predicate, $sequence)

[](#dropwhilepredicate-sequence)

Drops the longest sequence prefix of all items which satisfy the predicate

```
assert(['a', 'b', 'c', 4, 5, 6] === dropWhile('is_numeric', [1, 2, 3, 'a', 'b', 'c', 4, 5, 6]));
```

##### last($sequence)

[](#lastsequence)

Returns the last sequence item

```
assert(9 === last([1, 2, 3, 4, 5, 6, 7, 8, 9]));
```

##### partition($predicate, $sequence)

[](#partitionpredicate-sequence)

Returns two lists, one containing values for which the predicate returned true, and the other containing the items that returned false

```
assert([[1, 2, 3], ['a', 'b', 'c']] === partition('is_numeric', ['a', 1, 'b', 2, 'c', 3]));
```

##### span($predicate, $sequence)

[](#spanpredicate-sequence)

Returns two lists, one containing values for which your predicate returned true until the predicate returned false, and the other containing all the items that left

```
assert([[1], ['a', 2, 'b', 3, 'c']] === span('is_numeric', [1, 'a', 2, 'b', 3, 'c']));
```

##### indexed($sequence, $by, $keepLast = true, $transform = null)

[](#indexedsequence-by-keeplast--true-transform--null)

Returns array which contains indexed sequence items

`$by` is an array key or a function If `$keepLast` is true only the last item with the key will be returned otherwise a list of items which share the same key value will be returned `$transform` is a function that transforms list item after indexing

```
$indexedById = indexed([
    array('id' => 1, 'name' => 'John'),
    array('id' => 2, 'name' => 'Kate'),
    array('id' => 3, 'name' => 'Robert'),
], 'id');
```

##### sorted($sequence, $reversed = false, $key = null, $cmp = null)

[](#sortedsequence-reversed--false-key--null-cmp--null)

Returns array which contains sorted items from the passed sequence

If `$reversed` is true then return reversed sorted sequence. If `$reversed` is not boolean and `$key` was not passed then acts as a `$key` parameter `$key` is a function of one argument that is used to extract a comparison key from each item `$cmp` is a function of two arguments which returns a negative number, zero or positive number depending on whether the first argument is smaller than, equal to, or larger than the second argument

```
assert([1, 2, 3] === sorted([2, 3, 1]));
assert(['c', 'b', 'a'] === sorted(['c', 'a', 'b'], true));

$usersSortedByName = sorted($users, function($u) { return $u->getName(); });

// Which is the same as
use function \nspl\op\methodCaller;
$usersSortedByName = sorted($users, methodCaller('getName'));
```

Check more `\nspl\a\sorted` examples [here](https://github.com/ihor/Nspl/blob/master/examples/a_sorted.php).

##### keySorted($sequence, $reversed = false)

[](#keysortedsequence-reversed--false)

Returns array which contains sequence items sorted by keys

```
assert(array('a' => 1, 'b' => 2, 'c' => 3) === keySorted(array('b' => 2, 'c' => 3, 'a' => 1));
```

##### flatten($sequence, $depth = null)

[](#flattensequence-depth--null)

Flattens multidimensional sequence

```
assert([1, 2, 3, 4, 5, 6, 7, 8, 9] === flatten([[1, [2, [3]]], [[[4, 5, 6]]], 7, 8, [9]]));
assert([1, 2, [3], [4, 5, 6], 7, 8, 9] === flatten([[1, [2, [3]]], [[[4, 5, 6]]], 7, 8, [9]], 2));
```

##### pairs($sequence, $valueKey = false)

[](#pairssequence-valuekey--false)

Returns a list of (key, value) pairs. If `$valueKey` is true then returns (value, key) pairs.

```
assert([['a', 'hello'], ['b', 'world'], ['c', 42]] === pairs(array('a' => 'hello', 'b' => 'world', 'c' => 42)));
```

##### merge($sequence1, $sequence2)

[](#mergesequence1-sequence2)

Returns array containing `$sequence1` items and `$sequence2` items

```
assert([1, 2, 3, 4, 5, 6] === merge([1, 2, 3], [4, 5, 6]));
```

##### reorder(array $list, $from, $to)

[](#reorderarray-list-from-to)

Moves list item to another position

```
assert([2, 0, 1] === reorder([0, 1, 2], 2, 0)); // move item from the 2nd position to the begining of the list
```

##### value($array, $key, $default = null)

[](#valuearray-key-default--null)

Returns array value by key if it exists otherwise returns the default value

```
$data = array('a' => 1, 'b' => 2, 'c' => 3);
assert(2 === value($data, 'b', -1));
assert(-1 === value($data, 'd', -1));
```

##### values($sequence)

[](#valuessequence)

Returns list of the sequence values

```
assert([1, 2, 3] === values(array('a' => 1, 'b' => 2, 'c' => 3)));
```

##### keys($sequence)

[](#keyssequence)

Returns list of the sequence keys

```
assert(['a', 'b', 'c'] === keys(array('a' => 1, 'b' => 2, 'c' => 3)));
```

##### in($item, $sequence)

[](#initem-sequence)

Checks if the item is present in array or traversable object

```
assert(true === in(1, [1, 2, 3]);
```

##### diff($sequence1, $sequence2)

[](#diffsequence1-sequence2)

Computes the difference of arrays or traversable objects

```
assert([1] === diff([1, 2, 3], new ArrayObject([2, 3, 4]));
```

##### intersect($sequence1, $sequence2)

[](#intersectsequence1-sequence2)

Computes the intersection of arrays or traversable objects

```
assert([2, 3] === intersect([1, 2, 3], new ArrayObject([2, 3, 4]));
```

##### cartesianProduct($sequences)

[](#cartesianproductsequences)

Computes the cartesian product of two or more arrays or traversable objects

```
assert([
    [1, 'a'],
    [1, 'b'],
    [2, 'a'],
    [2, 'b'],
], cartesianProduct([1, 2], ['a', 'b']));
```

```
assert([
    array('hello' => 1, 'world' => 'a'),
    array('hello' => 1, 'world' => 'b'),
    array('hello' => 2, 'world' => 'a'),
    array('hello' => 2, 'world' => 'b'),
], cartesianProduct(array('hello' => [1, 2], 'world' => ['a', 'b'])));
```

##### isList($var)

[](#islistvar)

Returns true if the variable is a list

##### Chaining

[](#chaining)

It is possible to chain array function calls using the `with` function:

```
use function nspl\op\sum;

$square = function($n) { return $n * $n; };

$isEven = function($n) { return $n % 2 === 0; };

$sum = with(range(1, 5))
  ->filter($isEven)
  ->map($square)
  ->reduce(sum);

assert(20 === $sum);
```

##### Callbacks

[](#callbacks-2)

`nspl\a` provides all its functions as callbacks in its constants which have the same names as the functions.

```
use const \nspl\a\first;
assert([1, 2, 3] === map(first, [[1, 'a'], [2, 'b'], [3, 'c']]));
```

Check more `\nspl\a` examples [here](https://github.com/ihor/Nspl/blob/master/examples/a.php).

nspl\\a\\lazy
-------------

[](#nsplalazy)

Provides lazy versions of functions from [nspl\\a](#nspla)

This module might be useful when you don't need to process all the values from an array or any other traversable sequence. To understand how these lazy functions work let's have a look at the following example.

Let's define a function which wraps a generator function and logs all the values it yields. It will help up us to see the order of function calls:

```
// Calls generator function and logs the yielded values
function logged(callable $generatorFunction)
{
    static $count = 1;
    return function(...$args) use ($generatorFunction, &$count) {
        foreach ($generatorFunction(...$args) as $value) {
            echo $count++ . '. ' .  (string) $generatorFunction . ' -> ' . $value . "\n";
            yield $value;
        };
    };
}
```

To have some data to operate on, let's define a function which returns all natural numbers. Since it returns all the natural numbers it never terminates:

```
function naturalNumbers()
{
    $current = 1;
    while (true) yield $current++;
}
const naturalNumbers = 'naturalNumbers';
```

Also, let's define the operations we want to perform on those numbers:

```
// Returns square of a number
function square($n)
{
    return $n * $n;
}
const square = 'square';

// Checks if a number is even
function isEven($n)
{
    return $n % 2 === 0;
}
const isEven = 'isEven';
```

Now let's assume we want to take the first three even natural numbers and calculate their squares:

```
use const nspl\a\lazy\{take, map, filter};

$map = logged(map);
$take = logged(take);
$filter = logged(filter);
$numbers = logged(naturalNumbers)();

$evenNumbers = $filter(isEven, $numbers); // filter only even numbers
$firstThreeEvenNumbers = $take($evenNumbers, 3); // take only first 3 even numbers
$result = $map(square, $firstThreeEvenNumbers); // and calculate their squares

foreach ($result as $value) {
    echo "\nNext value is $value \n\n";
}
```

When we run this example we'll see the following output:

```
1. naturalNumbers -> 1
2. naturalNumbers -> 2
3. \nspl\a\lazy\filter -> 2
4. \nspl\a\lazy\take -> 2
5. \nspl\a\lazy\map -> 4

Next value is 4

6. naturalNumbers -> 3
7. naturalNumbers -> 4
8. \nspl\a\lazy\filter -> 4
9. \nspl\a\lazy\take -> 4
10. \nspl\a\lazy\map -> 16

Next value is 16

11. naturalNumbers -> 5
12. naturalNumbers -> 6
13. \nspl\a\lazy\filter -> 6
14. \nspl\a\lazy\take -> 6
15. \nspl\a\lazy\map -> 36

Next value is 36

```

If we used regular non-lazy versions of these functions, we would generate all the natural numbers, then filtered only even numbers, then took only the first three of them and then calculated their squares. Instead of that, you see that functions were called one by one passing the result to the next function until we completed the full cycle:

1. We took the first natural number – 1. It wasn't even, so we skipped it
2. We took the next one – 2, it was even
3. So it passed the `filter` function
4. It was the first number we took, so it passed through the `take` function as well
5. Then we calculated its square and printed the result

The same repeated on steps 6-10 and 11-15. On step 14 the `take` function took the last third number. So after step 15, when `map` requested the next value `take` didn't yield anything, and the whole iteration was finished.

Check this example [here](https://github.com/ihor/Nspl/blob/master/examples/a_lazy.php).

It possible to rewrite the code above using [chaining](#chaining):

```
$result = with(naturalNumbers())
    ->filter(isEven)
    ->take(3)
    ->map(square);
```

> **Tip**
>
> Note that while functions from `\nspl\a\lazy` allow you to avoid redundant computations, in case when you need to process all sequence values, functions from `\nspl\a` will do the job faster.

nspl\\args
----------

[](#nsplargs)

Helps to validate function arguments

##### expects($constraints, $arg, $atPosition = null, $otherwiseThrow = '\\InvalidArgumentException')

[](#expectsconstraints-arg-atposition--null-otherwisethrow--invalidargumentexception)

Checks that argument satisfies the required constraints otherwise throws the corresponding exception.

`$constraints` are callable(s) which return(s) true if the argument satisfies the requirements or it also might contain the required class name(s) If `$atPosition` is null, then the position is calculated automatically comparing given argument to the actual arguments passed to the function `$otherwiseThrow` defines exception which will be thrown if the given argument is invalid, it can be the exception class or exception object

```
use const \nspl\args\int;
use const \nspl\args\string;
use const \nspl\args\arrayAccess;
use function \nspl\args\expects;

function nth($sequence, $n)
{
    expects([arrayAccess, string], $sequence);
    expects(int, $n);

    return $sequence[$n];
}

nth('hello world', 'blah');
```

Outputs:

```
InvalidArgumentException: Argument 2 passed to nth() must be integer, string 'blah' given in /path/to/example.php on line 17

Call Stack:
    0.0002     230304   1. {main}() /path/to/example.php:0
    0.0023     556800   2. sqr() /path/to/example.php:17

```

##### expectsAll($constraints, array $args, array $atPositions = \[\], $otherwiseThrow = '\\InvalidArgumentException')

[](#expectsallconstraints-array-args-array-atpositions---otherwisethrow--invalidargumentexception)

Checks that all specified arguments satisfy the required constraints otherwise throws the corresponding exception.

```
use const \nspl\args\numeric;
use function \nspl\args\expects;

function sum($x, $y)
{
    expectsAll(numeric, [$x, $y]);

    return $x + $y;
}
```

##### expectsOptional($constraints, $arg, $atPosition = null, $otherwiseThrow = '\\InvalidArgumentException')

[](#expectsoptionalconstraints-arg-atposition--null-otherwisethrow--invalidargumentexception)

Checks that argument is null or satisfies the required constraints otherwise throws the corresponding exception.

```
function splitBy($string, $separator = ' ', $limit = null)
{
    expectsAll(string, [$string, $separator]);
    expectsOptional(int, $limit);

    return explode($separator, $string, $limit);
}
```

##### Predefined constraints

[](#predefined-constraints)

The module provides predefined constraints. Which can be one of the two types:

- OR-constraints which are evaluated with `or` operator (e.g. `expects([int, string], $arg)` evaluates as `$arg` has to be an `int` or a `string`)
- AND-constraints which are evaluated with `and` operator (e.g. `expects([string, longerThan(3), shorterThan(10)], $arg)` evaluates as `$arg` has to be a string longer than 3 characters and shorter than 10 characters). If you want to evaluate several AND-constraints as they were OR-constraints you can use `any` constraint. If you want to evaluate several OR-constraints as they were AND-constraints you can use `all` constraint

CallbackExplanationTypeboolChecks that argument is a boolORintChecks that argument is an intORfloatChecks that argument is a floatORnumericChecks that argument is numericORstringChecks that argument is a stringORarray\_Checks that argument is an arrayORobjectChecks that argument is an objectORcallable\_Checks that argument is callableORarrayKeyChecks that argument can be an array keyORtraversableChecks that argument can be traversed with foreachORarrayAccessChecks that argument supports array index accessORnonEmptyChecks that argument is not emptyANDpositiveChecks that argument is positive (&gt; 0)ANDnonNegativeChecks that argument is not negative (&gt;= 0)ANDnonZeroChecks that argument is not zero (!== 0)ANDany(constraint1, ..., constraintN)Checks constraints as if they were OR-constraintsANDall(constraint1, ..., constraintN)Checks constraints as if they were AND-constraintsANDnot(constraint1, ..., constraintN)Checks that argument does't satisfy all listed constraintsANDvalues(value1, ..., valueN)Checks that argument is one of the specified valuesANDlongerThan($threshold)Checks that string argument is longer than given thresholdANDshorterThan($threshold)Checks that string argument is shorter than given thresholdANDbiggerThan($threshold)Checks that number is bigger than given thresholdANDsmallerThan($threshold)Checks that number is smaller than given thresholdANDhasKey($key)Checks that argument supports array index access and has given keyANDhasKeys($key1, ..., $keyN)Checks that argument supports array index access and has given keysANDhasMethod($method)Checks that argument is an object and has given methodANDhasMethods($method1, ..., $methodN)Checks that argument is an object and has given methodsAND```
function setUsername($username)
{
    expects([string, longerThan(3), shorterThan(10)], $username);
    // ...
}

function setState($state)
{
    expects(values('running', 'idle', 'stopped'), $state);
    // ...
}
```

Duck-typing example:

```
class Service
{
    // ...
    public function setCache($cache)
    {
        expects(withMethods('set', 'get'), $cache);
        $this->cache = $cache;
    }
    // ....
}
```

##### Custom constraints

[](#custom-constraints)

It is possible to use custom constraints. Just define a new function which returns true when argument satisfies the constraint:

```
function even($value)
{
    return is_int($value) && $value %2 === 0;
}

function half($number)
{
    expects('even', $number);
    return $number / 2;
}
```

or we can make it more convenient to use introducing a constant:

```
const even = 'even';

function half($number)
{
    expects(even, $number);
    return $number / 2;
}

half('pie');
```

Outputs:

```
InvalidArgumentException: Argument 1 passed to half() must be even, string 'pie' given in /path/to/example.php on line 25

Call Stack:
    0.0009     253640   1. {main}() /path/to/example.php:0
    0.0123     673984   2. half() /path/to/example.php:25

```

If you need to create a constraint which takes arguments, you must create a callable object which implements `\nspl\args\Constraint` interface. It contains two methods:

- `__invoke($value)` - returns true if the value satisfies the constraint
- `__toString()` - returns text which will be used in the exception when the value doesn't satisfy the constraint. The text must contain a message which goes after "must" in the exception message.

nspl\\ds
--------

[](#nsplds)

Provides non-standard data structures and methods to work with them

##### DefaultArray

[](#defaultarray)

Array with a default value for missing keys. If you pass a function as default value it will be called without arguments to provide a default value for the given key, this value will be inserted in the array for the key, and returned. Using DefaultArray turns this code:

```
$a = array();
foreach([1, 2, 1, 1, 3, 3, 3] as $v) {
    if (!isset($a[$v])) {
        $a[$v] = 0;
    }
    ++$a[$v];
}
```

into this:

```
$a = defaultarray(0);
foreach([1, 2, 1, 1, 3, 3, 3] as $v) {
    ++$a[$v];
}
```

##### defaultarray($default, $data = array())

[](#defaultarraydefault-data--array)

Returns new DefaultArray

##### Set

[](#set)

An array-like collection that contains no duplicate elements. It supports basic set operations which take other sets, arrays and traversable objects as arguments

```
$set = set(1, 2);

$set->add('hello');
$set[] = 'world';

$set->delete('hello');

$array = [1, 2, 3];
$intersection = $set->intersection($array);

$anotherSet = Set::fromArray([1, 2, 3]);
$difference = $set->difference($anotherSet);

$iterator = new \ArrayIterator([1, 2, 3]);
$union = $set->union($iterator);

$isSubset = $set->isSubset([1, 2, 'hello', 'world']);

$isSuperset = $set->isSuperset([1, 2]);
```

##### set

[](#set-1)

Returns new Set

Check more `\nspl\ds` examples [here](https://github.com/ihor/Nspl/blob/master/examples/ds.php).

nspl\\rnd
---------

[](#nsplrnd)

##### randomString($length)

[](#randomstringlength)

Returns a random alpha-numeric string of the given length

##### choice($sequence)

[](#choicesequence)

Returns a random item from a non-empty sequence

##### weightedChoice($weightPairs)

[](#weightedchoiceweightpairs)

Returns a random item from a non-empty sequence of items with associated weights presented as pairs (item, weight)

```
use function \nspl\rnd\weightedChoice;
use function \nspl\a\pairs;

$nextPet = weightedChoice([['cat', 20], ['hamster', 30], ['dog', 50]]);
$nextFavouriteColor = weightedChoice(pairs(array(
    'red' => 0.2,
    'green' => 0.3,
    'blue' => 0.5,
)));
```

##### sample($population, $length, $preserveKeys = false)

[](#samplepopulation-length-preservekeys--false)

Returns a k length list of unique items chosen from the population sequence

Check more `\nspl\rnd` examples [here](https://github.com/ihor/Nspl/blob/master/examples/rnd.php).

nspl
----

[](#nspl)

##### getType($var)

[](#gettypevar)

Returns the variable type or its class name if it is an object

Roadmap
=======

[](#roadmap)

- Rewrite library using the latest features from PHP 7.2
- Move `nspl\args` into a separate module

Contributing
============

[](#contributing)

This project uses [semantic versioning](http://semver.org/) to tag releases. Please submit your pull requests to the latest release branch where the issue was introduced.

Feedback
========

[](#feedback)

There are no mailing lists or discussion groups yet. Please use GitHub issues and pull request or follow me on Twitter [@IhorBurlachenko](https://twitter.com/IhorBurlachenko)

###  Health Score

43

—

FairBetter than 91% of packages

Maintenance20

Infrequent updates — may be unmaintained

Popularity51

Moderate usage in the ecosystem

Community20

Small or concentrated contributor base

Maturity65

Established project with proven stability

 Bus Factor1

Top contributor holds 98.9% of commits — single point of failure

How is this calculated?**Maintenance (25%)** — Last commit recency, latest release date, and issue-to-star ratio. Uses a 2-year decay window.

**Popularity (30%)** — Total and monthly downloads, GitHub stars, and forks. Logarithmic scaling prevents top-heavy scores.

**Community (15%)** — Contributors, dependents, forks, watchers, and maintainers. Measures real ecosystem engagement.

**Maturity (30%)** — Project age, version count, PHP version support, and release stability.

###  Release Activity

Cadence

Every ~105 days

Recently: every ~140 days

Total

12

Last Release

2615d ago

PHP version history (2 changes)1.0PHP &gt;=5.4.0

1.3PHP &gt;=7.1.0

### Community

Maintainers

![](https://www.gravatar.com/avatar/73abba5ca14b1bc26d004398d23618fd1c60431eb4ced639b1bc56cfb9db6391?d=identicon)[ihor](/maintainers/ihor)

---

Top Contributors

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---

Tags

functionallazylodashphpramdaunderscorerandomgeneratorzipiteratorlistsplpythonfunctionalprogrammingpartialflattenweightedcurrymemoizepartial applicationweighted randomdefaultarrayhigher-orderitemGetterpropertyGettercurriedstandard php library

###  Code Quality

TestsPHPUnit

### Embed Badge

![Health badge](/badges/ihor-nspl/health.svg)

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```

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