It’s been said that structured programming is programming without GOTO, and functional programming is programming without assignment statements. Is declarative programming then programming without the concept of linear time?
Here's a functional example:
map (*3) [0,1,2,3,4,5,6,7,8,9]
Here's a fancier functional one:
getUser = User <$> getName <*> getEmail <*> getStartDate
If you answered "unspecified" then you're right! A compiler could parallelize either of these expressions!
But that's also true for imperative languages.
The problem is pretty easy to see in a C-style for loop:
for (int i = 0; i < 5; i++) {
printf("%d\n", i);
if (i % 2 == 0) i++;
}
Side effects and mutation break many of the promises provided by functional constructs. Hybrid languages like Python can illustrate this:
# pure, parallelizable
[2 * item for item in items]
# side effect! order matters!
[print(item) for item in items]
# side effect! order matters!
[arr.append(item) for item in items]
[f item | item <- items]What you wrote makes me think more of the point free style