Hello World in CrystalPublished on 28 February 2019 (Updated: 28 February 2019)
In this article, we’ll cover Hello World in Crystal.
How to Implement the Solution
With the background out of the way, let’s implement Hello World in Crystal:
puts "Hello, World!"
If we think back, we might remember that this syntax is exactly the same in Ruby. Of course, this should come as no surprise as Ruby’s syntax was a major influence on Crystal.
Digging through the API reveals that there are four definitions of puts:
def puts(*objects : _) : Nil def puts : Nil def puts(obj) : Nil def puts(string : String) : Nil
In our case, we’re using option four which simply writes a string to standard output.
Now, puts is pretty interesting because it automatically appends a new line unless a new line already exists. Personally, that’s the first time I’ve heard of a library call doing that kind of string formatting for the user. So, my question becomes: what happens if the string ends with multiple new lines?
Based on the source code:
def puts(string : String) : Nil self << string puts unless string.ends_with?('\n') nil end
The puts library appears to only remove the last new line. After running it, I can confirm that’s all this function does. Now, that’s some bizarre behavior:
puts 'Hello, World!' # Writes 'Hello, World!\n' puts 'Hello, World!\n' # Writes 'Hello, World!\n' puts 'Hello, World!\n\n' # Writes 'Hello, World!\n\n'
Honestly, I find this a little buggy. If, by default, this function adds a new line, then I would instinctively add a new line to the string (see line 2 above) to create extra space.
Of course, that doesn’t work. I suspect that Crystal style would prefer the following:
puts 'Hello, World!' puts
Or, something along those lines. At any rate, I’ve gone a bit too far down a rabbit hole. Let’s learn how to run our solution.1
How to Run the Solution
If we want to run our solution, perhaps the easiest thing to do is to copy our solution into the online Crystal editor. After that, we can hit run to see the output.
Alternatively, we can try to install the compiler on our system. However, I won’t bother going into that because I’m using a Windows PC which doesn’t appear to be supported.1
J. Grifski, “Hello World in Crystal,” The Renegade Coder, 26-Apr-2018. [Online]. Available: https://therenegadecoder.com/code/hello-world-in-crystal/. [Accessed: 28-Feb-2019]. ↩ ↩2