Published
Edited
Jun 2, 2020
Identity = {
const Identity = x => ({
emit: () => x, // other names: join, value, valueOf
chain: f => f(x),
map: f => Identity(f(x)),
inspect: () => `Identity(${x})`
});
Identity.of = x => Identity(x);
return Identity;
}
one = Identity(1)
one.emit()
one.chain(a => a + 1)
one.chain(add1)
{
const two = one.map(a => a + 1);
return [one.emit(), two.emit()];
}
{
const one = Identity(1)
const two = one.map(add1)
return two.inspect()
}
three = Identity.of(3)
List = {
const List = x => ({
emit: () => x,
chain: f => f(x),
map: f => List.of(f(x)),
inspect: () => `List(${x})`,
concat: a => List.of(x.concat(a)),
head: () => x[0]
});
List.of = arr => (arr instanceof Array ? List(arr) : Identity(arr));
return List;
}
myNumbers = List([1, 2, 3, 4, 5])
{
const b = myNumbers.concat([6, 7, 8, 9, 10]);
return b.inspect();
}
myNumbers.head()
myNumbers.head().inspect()
Maybe = {
const Just = x => ({
emit: () => x,
chain: f => f(x),
map: f => MaybeOf(f(x)),
fork: (_, g) => g(x),
isJust: true,
isNothing: false,
inspect: () => `Just(${x})`
});
const Nothing = x => ({
chain: _ => Nothing(),
emit: () => Nothing(),
map: _ => Nothing(),
fork: (f, _) => f(),
isJust: false,
isNothing: true,
inspect: () => 'Nothing'
});
const MaybeOf = x =>
x === null || x === undefined || x.isNothing ? Nothing() : Just(x);
return {of: MaybeOf}
}
convertReading = x => Maybe.of(x).map(fahrenheitToCelsius)
convertReading(reading1).inspect()
convertReading(reading2).inspect()
Maybe.of(reading1)
.map(fahrenheitToCelsius)
.fork(
_ => display('ERR!'),
t => display(`${t}°C`)
)
Maybe.of(reading2)
.map(fahrenheitToCelsius)
.fork(
_ => display('ERR!'),
t => display(`${t}°C`)
)
temp3C = Maybe.of(reading1)
.map(fahrenheitToCelsius)
.fork(
_ => display('ERR!'),
t => display(`${t}°C`)
)
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