Re: inject was Benchmark obsession?

On 06/21/2012 04:30 PM, Henry Maddocks wrote:
>
> On 21/06/2012, at 9:50 AM, Ryan Davis wrote:
>
>> Given #inject's other alias, #reduce, it is obvious that you don't 
>> use #inject for building up other objects. Even in a functional style 
>> of programming you'd _never_ see it building up anything. You'd see 
>> it REDUCING (folding) an object. If #inject is applied in a 
>> non-folding manner, it isn't functional, it is just dumb. Don't 
>> pretend otherwise (and if you do pretend otherwise, go read more 
>> books on lisp--start with SICP). The second I see a semicolon (or 
>> return) in an inject, I immediately suspect that someone is writing 
>> clevar/stupid code.
>>
>> I don't have any recent examples from the list, but I'm on record in 
>> multiple mediums ranting against people who use #inject improperly. 
>> I'll make up one based on examples I've seen time and time again:
>
> I come across this quite often, especially in Rails apps.
>
> a = {:list => [1,2,3,4]}
> b = {:list => [9,8,7,6,5]}
>
> c = [a,b]
>
> c.inject([]) {|memo, run| memo + run[:list] }
>
> I always cringe when I see it but I haven't found an alternative that 
> is as clear and concise.
> collect and flatten looks ugly. I'd love to be able to do...
>
> c.collect {|run| *run[:list]}
>
>
> Henry

You could move the array outside:

a = {:list => [1,2,3,4]}
b = {:list => [9,8,7,6,5]}

c = [a,b]

all = []

c.each { |h| all.concat h[:list] }

Saves a little memory, too?

-Justin