Magical, Mystical JavaScript Transducers

Re:Magical, Mystical JavaScript Transducers by agumonkey on Saturday June 29, 2019 @03:19AM (#20311268)

The article obfuscates the point. Reducers/transducers are from the FP world. In FP avoiding mutable state is one the main point.

    dot = field => obj => obj[field]                        // unsafe
    Array.average = self -> reduce(add, self) / self.length // unsafe
    slang.filter(s -> s.popularity > 0)
         .map(dot('popularity'))
         .average()

Bonus points:

    - no state
    - reusable pure functions
    - a tad shorter
    - maybe as readable as the `for over state` idiom ? (depending on habits)

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Re:Magical, Mystical JavaScript Transducers by chris_st on Saturday June 29, 2019 @08:17AM (#20312149)

Downside: Still going over the array multiple times.

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Re:Magical, Mystical JavaScript Transducers by sli on Monday July 01, 2019 @03:09PM (#20328685)

You could (usually, but not always) compose the functions you're passing into filter and map and use reduce instead to do both operations in a single pass.

(Edit: This is a big point in the article -- apologies, I hadn't finished reading it yet.)

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Re:Magical, Mystical JavaScript Transducers by agumonkey on Saturday June 29, 2019 @09:03AM (#20312346)

fair point, in js it will, in other languages that idiom gets deforested into a single pass though

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Re:Magical, Mystical JavaScript Transducers by chris_st on Saturday June 29, 2019 @06:03PM (#20315074)

Cool, which languages do this?

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Re:Magical, Mystical JavaScript Transducers by cofunctor on Saturday June 29, 2019 @06:30PM (#20315211)

This ought to work with any lazy language (or lazy data structure), which is one of the huge benefits of laziness for FP.

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