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Discussion on: JavaScript Conditional Branching

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Replies for: clever, I had to stare at it for a few minutes to go through all the possibilities. That's where the real beauty of a neatly syntaxed pattern matc...

 
peerreynders profile image
peerreynders •

I had to stare at it for a few minutes to go through all the possibilities.

That's possibly because of lack of familiarity.

The Rust equivalent doesn't look that different to me:

fn categorize(mut sides: [T; 3]) -> Option<Category> {
    sides.sort_unstable_by(|a, b| a.partial_cmp(b).unwrap());
    let [a, b, c] = sides;
    let is_triangle = a + b > c;
    if is_triangle {
        Some(match (a.eq(&b), b.eq(&c)) {
            (true, true) => Equilateral,
            (true, _) | (_, true) => Isoceles,
            _ => Scalene,
        })
    } else {
        None
    }
}
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in particular

match (a.eq(&b), b.eq(&c)) {
    (true, true) => Equilateral,
    (true, _) | (_, true) => Isoceles,
     _ => Scalene,
}
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In Erlang (and Elixir is similar) something like (again, assuming that the sides are sorted by length so that equal sides will always be adjacent)

case Sides of
  {A, A, A} -> "equilateral";
  {A, A, C} -> "isosceles"; 
  {A, B, B} -> "isosceles";
  _ -> "scalene"   
end.
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or

case Sides of
  {A, B, C} when A == B andalso B == C -> "equilateral";
  {A, B, C} when A == B orelse B == C -> "isosceles"; 
  _  -> "scalene"
end.
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ReScript (aka ReasonML; JavaScript flavored OCaml)

let kind = switch (a === b, b === c) {
| (true, true) => "equilateral"
| (true, _) | (_ , true) => "isosceles"
| _  => "scalene"
}
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etc.

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robertseidler profile image
RobertSeidler • • Edited

That's possibly because of lack of familiarity.

very likely.

And nice overview, of how different languages handle the same problem