Hop

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Higher order predicates library.

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What?

A "higher order function" is a function that either returns a function or takes a function as argument.

A "functional predicate" is a function that receives one or more arguments (subject) and returns true or false.

This library is a collections of functions that return functional predicates.

Why?

In PHP there are some functions like array_map, array_filter, and so on, that take a functional predicate as argument.

For example:

$data = [
  'foo',
  1,
  true,
  'bar',
  [],
  ''
];

$strings = array_filter($data, 'is_string'); // ['foo', 'bar', '']

This can be done thanks to the fact that a is_string is a named function.

But if we need something more complex, e.g. we also want to strip empty strings, we need to:

$strings = array_filter($data, function($item) {
    return is_string($item) && $item !== '';
});

One of the functions of this library is isType() that accepts a string representing a type and returns a predicate that can be used to check subjects against that type.

Another of the functions of this library is isNotEmpty() that returns a predicate that verifies non-empty values.

Another function is chain() that takes an arbitrary number of predicates and returns a predicate that returns true when all the given predicates return true.

Using these 3 functions the code above can be written like this:

$strings = array_filter($data, Hop\chain(Hop\isType('string'), Hop\isNotEmpty()));

All the functions in this library are in Hop namespace.

Installation

Served by Composer using toobo/hop.

List of functions

Here a list of all the functions currently provided by library (namespace omitted):

General

• always() Return a predicate that always return true
• never() Return a predicate that always return false
• isEmpty()
• isNotEmpty()
• isTrueish()
• isFalsey()
• isBooleanLooking()

Comparison

• is($value)
• isNot($value)
• equals($value)
• notEquals($value)
• matches(string $regex)
• notMatches(string $regex)
• moreThan(int|float $limit)
• moreThanOrEqual(int|float $limit)
• lessThan(int|float $limit)
• lessThanOrEqual(int|float $limit)
• between(int|float $min, int|float $max)
• betweenInner(int|float $min, int|float $max)
• betweenLeft(int|float $min, int|float $max)
• betweenRight(int|float $min, int|float $max)

Type check

• isType(string $type) Works with scalar types, classes and interfaces
• objectIs(string $classOrInterface) Works with objects

Var filtering check

• filterVar(int $filter, $options = null) Returns a predicate that applies filter_var() to subject using given filter and options.
• isEmail()
• isUrl()
• isIp()
• isMac()

Size check

• size(int $size) Verify elements count of arrays and countable objects and string length
• smallerThan(int $size)
• smallerThanOrEqual(int $size)
• biggerThan(int $size)
• biggerThanOrEqual(int $size)
• sizeBetween(int $min, int $max)
• sizeBetweenInner(int $min, int $max)
• sizeBetweenLeft(int $min, int $max)
• sizeBetweenRight(int $min, int $max)

Elements check (for arrays and strings)

• contains(string $subString) Verify a string contains a sub-string
• startsWith(string $subString) Verify a string starts with a sub-string
• endsWith(string $subString) Verify a string ends with a sub-string
• has($item) Verify an string contains an item
• headIs(...$items) Verify first item(s) of an array
• tailIs(...$items) Verify last item(s) of an array
• in(...$items) Verify an item is one of given items
• notIn(...$items) Verify an item is none of given items
• intersect(...$items) Verify an array has an non-empty intersection with given items
• notIntersect(...$items) Verify an array has an empty intersection with given items

Array keys

• hasKey(string $key)
• hasNotKey(string $key)
• hasAllKeys(string ...$keys)
• hasAnyOfKeys(string ...$keys)
• hasNoneOfKeys(string ...$keys)
• hasNotAllKeys(string ...$keys)
• valueForKeyIs(string $key, $value)
• valueForKeyIsNot(string $key, $value)
• applyOnValueForKey(string $key, callable $callback)

Object methods

• hasMethod(string $method)
• classHasMethod(string $method)
• methodReturns(string $method, $value, ...$params)

Predicates composition

• not(callable $predicate) Negate given predicate
• chain(callable ...$predicates) Combine predicates in AND mode
• pool(callable ...$predicates) Combine predicates in OR mode

Misc

• applyAfter(callable $transformation, callable $predicate) Returns a predicate which returns the result of the predicate, after it has been applied the input value, transformed by the $transformation function.
• applyAfterMethod(string $method, callable $predicate)

License

Hop is open source and released under MIT license. See LICENSE file for more info.