Right, and the Python errors mention all sorts of things a beginner is not expected to understand, like "builtin_function_or_method". I don't think "understanding builtin_function_or_method" is required to write the Python and I don't think "understanding Monad" is required to write the Haskell.
> If our requirements changed to now read and sum an arbitrary number of inputs together, I'd expect a beginner could change the Python program to do so. I'm skeptical they could make the required changes to the Haskell version (without understanding monads).
Where do I have to "understand monads" to write this?
main = do
iters <- readLn
let loop n total =
if n == iters
then print total
else do
x <- readLn
loop (n + 1) (total + x)
loop 0 0
def main():
iters = input()
total = 0
for _ in range(iters):
x = input()
total += x
print total
main2 = do
iters <- readLn
total <- newIORef 0
for_ [1..iters] $ \_ -> do
x <- readLn
modifyIORef' total (+ x)
theTotal <- readIORef total
print theTotal
Now, if I were writing this for real I probably would use a version with a state monad transformer so it was
main3 = do
iters <- readLn
total <-
flip runStateT 0 $ for_ [1..iters] $ \_ -> do
x <- lift readLn
modify' (+ x)
print total
[1] https://www.cs.cornell.edu/courses/cs3110/2018sp/l/14-mutabl...
This isn't the case in Python where input and output are standard functions. The syntax for function declaration and variable assignment just work.
If our requirements changed to now read and sum an arbitrary number of inputs together, I'd expect a beginner could change the Python program to do so. I'm skeptical they could make the required changes to the Haskell version (without understanding monads).