Functional programming is not popular because it is weird (2016)

Re:Functional programming is not popular because it is weird... by qsort on Tuesday September 14, 2021 @02:07AM (#28520871)

Java streams are a (limited) version of what you propose. Something like this is very idiomatic:

    myhashmap.entrySet()
        .stream()
        .map(Map.Entry::getValue)
        .sorted()
        .distinct()
        .toList()

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Re:Functional programming is not popular because it is weird... by kilotaras on Tuesday September 14, 2021 @03:46AM (#28521584)

Difference with pipe operator would be

1. can't be extended.

    myhashmap.entrySet()
       .stream()
       .flattenBars()
       .toFoo()

2. (As a result of 1) - applies only to streams

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Re:Functional programming is not popular because it is weird... by qsort on Tuesday September 14, 2021 @04:45AM (#28521963)

> can't be extended

They can be extended arbitrarily by defining collectors. The Stream interface is very well designed. For example your "toFoo" would be .collect(Collector(<foo-provider>, <foo-accept>, <foo-merge>, <foo-finisher>)). All of them can be arbitrary functions working on arbitrary types. That's the standard library implementation of "toList", in fact!

> applies only to streams

You're exactly correct here, but for legacy reasons Java did not have a choice. I'm the first to admit mylist.stream().map(f).toList() is dumb. A list is a functor, dammit!

It's the best possible solution given the existing constraints, but it's definitely limited in what it can do.

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Re:Functional programming is not popular because it is weird... by carlmr on Tuesday September 14, 2021 @02:40AM (#28521126)

I was going to say C# LINQ, too!

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