How can I write a code that shows the common divisors of two numbers?

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a code that finds common divisors of two numbers

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Shouldn’t you be using google instead of the dev forum for this sort of question?

Pretty sure most math questions have been answered before and programmed by someone else unless it’s a real tough one.

In this case I searched “lua common divisors of two numbers” and found the function already written.

--[[ Functional Programming Example -- Greatest Common Divisor
     H. Conrad Cunningham, Professor
     Computer and Information Science
     University of Mississippi

Developed for CSci 658, Software Language Engineering, Fall 2013

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2013-09-08: Completed prototype

This greatest common divisor (gcd) function is adapted from section
1.2.5 of Abelson and Sussman's Structure and Interpretation of
Computer Programs (SICP) textbook.

--]]


-- Function "gcd" computes the greatest common divisor of its two
-- nonegative number arguments using Euclid's algorithm. It is based
-- on property: If r is the remainder of a divided by b, then the
-- common divisors of a and b are precisely the same as the common
-- divisors of b and r.  
-- Time complexity:  O(log max(a,b))
-- Space complexity: O(1) with tail call optimization

local function gcd(a,b)
  if type(a) == "number" and type(b) == "number" and 
        a == math.floor(a) and b == math.floor(b) then
    if b == 0 then
      return a
    else
      return gcd(b, a % b) -- tail recursion
    end
  else
    error("Invalid argument to gcd (" .. tostring(a) .. "," .. 
          tostring(b) .. ")", 2)
  end
end

https://john.cs.olemiss.edu/~hcc/csci658/notes/SICP_examples/Lua/gcd.lua

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okay maybe i could forget to search before post.

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