You can solve the (potential) strictness problem like this:

  | (iterator < exponent) = result `seq` modLoop (iterator + 1) exponent (mod (result * base) modulus)

but you'd be better off changing your function to use exponentiation by squaring, which will dramatically reduce the number of multiplications.

On Sat, Feb 20, 2021, 7:36 PM A. Mc. <47dragonfyre@gmail.com> wrote:
Hello,

I'm just starting off, but I'm wondering if anyone has any suggestions.  I've made a recursive function that's goal is to handle a base raised to a very large power.  
modLoop :: Integer -> Integer -> Integer -> Integer -> Integer -> Integer
modLoop iterator exponent result base modulus
  | (iterator == exponent) = result
   | (iterator < exponent) = modLoop (iterator + 1) (exponent) (mod (result * base) modulus) base modulus
   | (iterator > exponent) = (-1)

However, it flat breaks or takes a long time when using large numbers.

I need to get better at using strict functions, however, I compiled with ghc -o (as it tends to implement the strict version - ?) and I still have the same problem.  What's a better way?

Thanks in advance and thank you for your time.
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