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Programming-Idioms

  • Lua
  • Rust

Idiom #20 Return two values

Implement a function search which looks for item x in a 2D matrix m.
Return indices i, j of the matching cell.
Think of the most idiomatic way in the language to return the two values at the same time.

fn search<T: Eq>(m: &Vec<Vec<T>>, x: &T) -> Option<(usize, usize)> {
    for (i, row) in m.iter().enumerate() {
        for (j, column) in row.iter().enumerate() {
            if *column == *x {
                return Some((i, j));
            }
        }
    }

    None
}

This returns an optional tuple.
function search(m, x)
   for i,v1 in ipairs(m) do
      for j,v2 in ipairs(v1) do
         if v2 == x then return i,j end
      end
   end
end

Lua functions may return multiple results
type Matrix is array (Positive range <>, Positive range <>) of Integer;

function Search (M : Matrix; X : Integer; I, J : out Integer) return Boolean is
begin
   for K in M'Range (1) loop
      for L in M'Range (2) loop
         if M (K, L) = X then
            I := K;
            J := L;
            return True;
         end if;    
      end loop;
   end loop;

   return False;
end Search;

New implementation...
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