Added measure-elapsed-time example

[AlexEne]

I just explored a bit this repo, read the contribution guidelines, one thing lead to another and I added the measure-elapsed-time example.

fixes #341

[budziq]

Thanks @AlexEne !
Please find some cosmetic suggestions below.

[budziq]

Thanks @AlexEne !
Please find some cosmetic suggestions below.

[budziq]

Lets hide the parts of the example that are not directly related to actual measurement with leading #

# use std:thread
# 
# fn expensive_function() {
# thread::sleep(Duration::from_millis(10));
# }

[budziq]

I wouldn't exactly say that it's profiling nor benchmarking (there are better and easier ways to benchmark built into rust nightly or available in crates.io for stable), actually I would not like to even suggest that this is even a dirty form of either one of these. Rather just an elapsed time reporting that is also useful in some cases.

I'd suggest to remove or rewrite this last two paragraphs.

[AlexEne]

Ok, I missed the point a bit since the description was a bit generic. I will do a PR with these fixes later today.

[budziq]

start() is not callable, this is why the CI complains

[AlexEne]

Ah, I see, I believed that it has to be a full rust program so it compiles (with main and all that)

[budziq]

I'd remove this second approach all together.

[AlexEne]

Done

[budziq]

Let's reformat the description somewhat to a form like "Measures [time::Instant::elapsed] since [time::Instant::now]"

[budziq]

One possible tripwire here is that elapsed does not reset the start in any way.

We can suggest following or just mention the fact in the description.

let start = Instant::now();
expensive_function();
let (start, duration) = (Instant::now(), start.elapsed());
println!("Time elapsed in expensive_function() is: {:?}", duration);
some_other_function();
println!("Time elapsed in some_other_function() is: {:?}", start.elapsed());

[AlexEne]

I will just mention it in the description since I think this example will be a bit harder to follow and since start is reset before the println!(), makes it a bit imprecise.

[budziq]

Thanks @AlexEne !

Please also checkout #209 and comment there if you consent to repository re-license to CC0.

[AlexEne]

I commented on that thread, I agree with the idea and thanks for all the feedback ;)

[budziq]

Thanks! Not that much feedback was needed :)