Return to Answer

result = 0
for num in numbers:
    if pred(result):
        result += num
return result

result = 0
for num in numbers:
    if pred(num):
        result += num
return result

###What is it in functional programming that makes a difference?

###So, are variables and loops wrong?

###Summary

What is it in functional programming that makes a difference?

So, are variables and loops wrong?

Summary

sum pred list = 
    case pred of
        [] -> 0
        h:t -> if pred h then h + sum pred t
                         else sum pred t

Variables are inherently imperative, explaining how instead of what, and giving little prediction of what their value may be a few lines later or after a few loop iterations. Loops generally require state to make sense, and so they are inherently imperative as well. But there are many things that are much easier explained by them, and many algorithms that require mutable state to be fast.

sum pred list = 
    case list of
        [] -> 0
        h:t -> if pred h then h + sum pred t
                         else sum pred t

There are many things that are much easier explained by them, and many algorithms that require mutable state to be fast. But variables are inherently imperative, explaining how instead of what, and giving little prediction of what their value may be a few lines later or after a few loop iterations. Loops generally require state to make sense, and so they are inherently imperative as well.