From: Brian Candler <lists@...>
Date: 2012-09-15T05:40:55+09:00
Subject: Re: inject is pathetic?

Josh Cheek wrote in post #1075977:
> But in Ruby
>
> strings.inject("") { |joined, current| joined + current }
>
> is slow and wasteful because it created all the intermediate forms: "",
> "a", "ab", "abc", "abcd", "abcde"
> Whereas each_with_object only creates: "abcde"

Correct, in ruby, because ruby isn't optimised for funtional use. 
Another example is that there is no tail-recursion unless you build ruby 
with a special compile-time option.

But in other languages, what you've written is actually efficient. For 
example, Erlang has a specific optimisation for binaries which are 
appended to, where no reference remains to the previous incarnation of 
the binary.

> Your example is compelling to you, because you're enamored with the
> implementation

I'd say the opposite; in ruby the implementation is not so good, but 
it's the concept, the abstraction, which is attractive.

foo.each => do something for each element of an array
foo.inject => calculate a summary value across all elements of an array

In fully functional languages, foo.each makes no sense because "do 
something" makes no sense - functions don't have side-effects. (Erlang 
is *not* such a language, by the way, but is part way because it doesn't 
have mutable variables).

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