Re: Is there any particular reason for using this form?

[David Nolen]

It is necessary - integer literals default to primitive long and I'm not sure if >= will inline if it doesn't have type information in scope. This bit of noise could probably be removed by improving type inference in the compiler.

On Thu, May 16, 2013 at 3:09 PM, Pavel Prokopenko <pavel.a.p...@gmail.com> wrote:

Hi,

I've been reading Clojure sources in order to get a better understanding of how and why things work and found this implementation of nth function in src/clj/clojure/gvec.clj:

  (nth [this i not-found]
       (let [z (int 0)]
         (if (and (>= i z) (< i (.count this)))
           (.nth this i)
           not-found)))

The question might sound weird, but anyway..  Is there any reason for doing so instead of:

  (nth [this i not-found]
         (if (and (>= i 0) (< i (.count this)))

           (.nth this i)
           not-found))



or is it just a matter of taste? I'm just curious because the first form seems more verbose and doesn't improve readability, though it's not complex either.

Thanks.

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[Pavel Prokopenko]

Thanks, David!

What about (.nth this i) vs (nth this i)? Is that also some optimization trick like direct object's method call vs reflection method call?

[David Nolen]

.nth is a method call, nth is a function call. Another perf thing.

In anycase if you're looking for examples of everyday Clojure it's best to look elsewhere :) fast Clojure tends to look a bit quirky and relies on details of the current state of the compiler.

--

[David Nolen]

On Thu, May 16, 2013 at 4:30 PM, David Nolen <dnolen...@gmail.com> wrote:

.nth is a method call, nth is a function call. Another perf thing.

In anycase if you're looking for examples of everyday Clojure it's best to look elsewhere :) fast Clojure tends to look a bit quirky and relies on details of the current state of the compiler.

And by "fast" I mean code that for some reason or another needs to reach the best performance offered by the host. These sorts of tricks are not necessary to write reasonably efficient everyday code IMO.