[SOLVED] Repeat value infinitely Ramda

Repeat value infinitely Ramda

For zipping, how can I zip a list with repetitions of a single value?

desired:

R.zip([1, 2, 3])(R.repeat(2)); // [[1, 2], [2, 2], [3, 2]]

Solution

You can use R.ap as a combinator of the R.zip function and a function that takes the length, and repeats and item:

const { ap, zip, pipe, length, repeat } = R

const fn = item => ap(
  zip,
  pipe(length, repeat(item))
)

const result = fn(2)([1, 2, 3])

console.log(result)

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This an overkill, but just for the sake of completeness - you can create Infinite lazy arrays in JS using a proxy. Create an array proxy with a get trap. For length return Infinity, and call a cb function to generate an item. In this case I use R.always to create always return 2 for an item:

const { zip, __, always } = R

const getInfiniteArray = getItem => new Proxy([], {
  get(target, prop, receive) {
    return prop === 'length' 
      ? Infinity
      : getItem(target, prop, receive)
  }
})

const fn = zip(__, getInfiniteArray(always(2)))

const result = fn()([1, 2, 3])

console.log(result)

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