Source code in the seed7 programming language

$ include "seed7_05.s7i";

$ syntax expr: .().dot.() is  -> 6;  # priority of dot operator

const func integer: (in array integer: a) dot (in array integer: b) is func
  result
    var integer: sum is 0;
  local
    var integer: index is 0;
  begin
    if length(a) <> length(b) then
      raise RANGE_ERROR;
    else
      for index range 1 to length(a) do
        sum +:= a[index] * b[index];
      end for;
    end if;
  end func;
 
const proc: main is func
  begin
    writeln([](1, 3, -5) dot [](4, -2, -1));
  end func;