4 ms·

It was popular in the 90s and early 00s to apply OOP techniques to everything, whether or not it made any sense. Today we use value types and higher-order func

It was popular in the 90s and early 00s to apply OOP techniques to everything, whether or not it made any sense. Today we use value types and higher-order functions all over the place, we customize objects with composition instead of inheritance, and we use module boundaries for encapsulation. It doesn't help that it's easy to overdo your taxonomy, or try to model objects after the "real world" (rather than your domain model). Examples in some textbooks are pretty bad... if "dog" inherits from "animal" then you should throw the book out.

seanmcdirmid 12y ago
I would rather throw the book out if they had "dog" inheriting from "vehicle." Really, metaphors and analogies are nice, one of the most powerful parts of our capacity for human language. Just because math lacks those concepts, and so the same isn't possible in a functional mindset, doesn't mean it is bad. Some FP textbooks are pretty bad...if fibanocci is implemented with just recursion, then you should throw the book out. </s>
- dietrichepp 12y ago
  My problem with "dog" and "animal" is not that I hate metaphors, but because the example tends to teach students that "X is a Y" is justification for "class X inherits from class Y". It's also usually found in books that focus more on the hammer than on the nails, if you know what I mean. Recursive fib is usually taught to show how a naive translation of a recursive formula into code can cause poor performance. I can't think of a better example.
  - seanmcdirmid 12y ago
    Reclusive FP is usssually the first example of the FP textbook, and is used to teach how elegant FP is from the beginnin jn spite of the fact that you should never write that (and who needs to write fib anyways). Inheritance is subtyping at the basic level: we all know a dog is an animal, and that all animals share a common ancestor. It is a crude instrument, especially in Java, and often can't be used, but not because the concept of extension is flawed in some ways. If you had traits/mixins, extension can be used much more widely. I'm just as annoyed at the ideological "composition, not inheritance" crowd. The truth is, one has to learn a bunch of generalizations and then practice a lot to get it; good design is just hard to teach in a book.

seanmcdirmid 12y ago

I would rather throw the book out if they had "dog" inheriting from "vehicle." Really, metaphors and analogies are nice, one of the most powerful parts of our capacity for human language. Just because math lacks those concepts, and so the same isn't possible in a functional mindset, doesn't mean it is bad. Some FP textbooks are pretty bad...if fibanocci is implemented with just recursion, then you should throw the book out. </s>

dietrichepp 12y ago
My problem with "dog" and "animal" is not that I hate metaphors, but because the example tends to teach students that "X is a Y" is justification for "class X inherits from class Y". It's also usually found in books that focus more on the hammer than on the nails, if you know what I mean. Recursive fib is usually taught to show how a naive translation of a recursive formula into code can cause poor performance. I can't think of a better example.
- seanmcdirmid 12y ago
  Reclusive FP is usssually the first example of the FP textbook, and is used to teach how elegant FP is from the beginnin jn spite of the fact that you should never write that (and who needs to write fib anyways). Inheritance is subtyping at the basic level: we all know a dog is an animal, and that all animals share a common ancestor. It is a crude instrument, especially in Java, and often can't be used, but not because the concept of extension is flawed in some ways. If you had traits/mixins, extension can be used much more widely. I'm just as annoyed at the ideological "composition, not inheritance" crowd. The truth is, one has to learn a bunch of generalizations and then practice a lot to get it; good design is just hard to teach in a book.