Reader

Environment variables, like impure I/O operations, have the capacity to break function purity. The Reader monad is a solution to interacting with an external environment - that inclusive of data with wide-reaching configuration value. The monad localizes state changes dependent on the said data to ensure that functions are kept pure.

reader

reader(operation)

reader :: (r -> a) -> m a

Puts a value in a Reader environment - calls the Reader monad constructor and initializes a value of type Reader.

Since:

• bingo-functional - v1.11.0
• bingo-functional-js - v0.1.0

Argument(s):

• operation - Operation to put in the Reader environment

JavaScript

import { reader, partial, concat } from 'bingo-functional-js'
const hello = reader(partial(concat, ' ', 'Hello,'))

PHP

use Chemem\Bingo\Functional as f;use function Chemem\Bingo\Functional\Functors\Monads\Reader\reader;
$hello = reader(f\partial(f\concat, ' ', 'Hello,'));

runReader

runReader(reader, value)

runReader :: Reader r a -> r -> a

Applies an arbitrary value to a Reader and extracts a value from it.

Since:

• bingo-functional - v1.11.0
• bingo-functional-js - v0.1.0

Argument(s):

• reader - Instance of Reader monad
• value - Arbitrary value applied to Reader monad

JavaScript

import { reader, partial, concat, runReader } from 'bingo-functional-js'
const hello = reader(partial(concat, ' ', 'Hello,'))
runReader(hello, 'Mike')

PHP

use Chemem\Bingo\Functional as f;use function Chemem\Bingo\Functional\Functors\Monads\Reader\{  reader,  runReader};
$hello = reader(f\partial(f\concat, ' ', 'Hello,'));
runReader($hello, 'Mike');

mapReader

mapReader(function, reader)

mapReader :: (a -> b) -> Reader r a -> a -> Reader r b

Applies a function to value in a Reader environment.

Since:

• bingo-functional - v1.11.0
• bingo-functional-js - v0.1.0

Argument(s):

• function - An arbitrary function
• reader - A Reader monad instance

JavaScript

import {  reader,  concat,  partial,  mapReader,  runReader,} from 'bingo-functional-js'
const hello = reader(partial(concat, ' ', 'Hello,'))
const res = mapReader('strtoupper', hello)
runReader(res, 'Mike')

PHP

use Chemem\Bingo\Functional as f;use function Chemem\Bingo\Functional\Functors\Monads\Reader\{  reader,  mapReader,  runReader};
$hello  = reader(f\partial(f\concat, ' ', 'Hello,'));
$res    = mapReader('strtoupper', $hello);
runReader($res, 'Mike');

withReader

withReader(function, reader)

withReader :: (r -> r') -> Reader r a -> Reader r' a

Executes a computation in a modified Reader environment.

Since:

• bingo-functional - v1.11.0
• bingo-functional-js - v0.1.0

Argument(s):

• function - An arbitrary function
• reader - A Reader monad instance

JavaScript

import {  reader,  concat,  partial,  mapReader,  runReader,} from 'bingo-functional-js'
const hello = reader(partial(concat, ' ', 'Hello,'))
const ask = withReader(  (greet) =>    reader((name) => `${greet}.${name === 'world' ? '' : ' How are you?'}`),  hello,)
runReader(ask, 'Mike')

PHP

use Chemem\Bingo\Functional as f;use function Chemem\Bingo\Functional\Functors\Monads\Reader\{  reader,  withReader,  runReader};
$hello  = reader(f\partial(f\concat, ' ', 'Hello,'));
$ask    = withReader(  fn (string $greet) => reader(fn (string $name) => (    f\concat('', $greet, '.', $name === 'world' ? '' : ' How are you?')  )),  $hello);
runReader($ask, 'Mike');

ask

ask()

ask :: m r

Retrieves the Reader monad environment.

Since:

• bingo-functional - v1.11.0
• bingo-functional-js - v0.1.0

Argument(s):

None

JavaScript

import { ask } from 'bingo-functional-js'
const result = ask()

PHP

use function Chemem\Bingo\Functional\Functors\Monads\Reader\ask;
$result = ask();