In my job search, I was issued a coding challenge last week, and needed to learn the basics of several languages I’m not familiar with. I’m not sure they use some of those regularly on the job – seems they just wanted to see if I could flexibly catch on.
The challenges themselves were very easy to solve. The first one was a slightly modified FizzBuzz challenge in Haskell, and the second one was spotting palindromes, and sorting text, in each of the other 3 languages.
One thing that stuck out to me was the differences/similarities of taking a file path as a command line argument in Rust, Python, and Swift.
In Rust, you need std::env, std::fs::File, and std::fs::BufReader. Then you can grab your arguments and put them into an array, and then select the path from the array, open the file, and read it, like this:
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let args: Vec<_> = env::args().collect();
let filepath = &args[1];
let f = File::open(filepath).unwrap();
let file = BufReader::new(&f);
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In Python you only need to import sys, and you can do the following:
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filepath = sys.argv[1]
with open(filepath) as fp:
for num, line in enumerate(fp):
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Then under that, you can say what you want to do for each line in that file. I implemented the same behavior in Rust, but took more code than I showed in the above example. In Python, it’s much simpler, so it’s included here.
Finally, in Swift, it’s somewhere in between. I did the following to collect the argument I wanted:
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private let arguments: [String]
public init(arguments: [String] = CommandLine.arguments) {
self.arguments = arguments
}
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Then within a public func, I had this:
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let fileName = arguments[1]
do {
let contents = try NSString(contentsOfFile: fileName,
encoding: String.Encoding.ascii.rawValue)
contents.enumerateLines({ (line, stop) -> () in
*CODE FOR EACH LINE HERE*
})
}
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It took a bit of time to figure out the ins and outs of how to do this in each language, but lucky for me, reading individual lines from a file is pretty commonly done in all languages. I was able to read a lot of explanations on how other people have done it, and why they did it that way. No one I saw was trying to do the same thing I was, but reading lines from a file can be pretty universal! I’m glad for all the great documentation online – especially when learning to use a new programming language.