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The use of `class` for things that should be simple free functions

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Re: The use of `class` for things that should be simple free functions

#61

Post by edflsafoiewq »

amw-zero wrote: post #48
dataflow wrote: post #18

Counter-point: while in many situations this isn't the right approach, it's worth recognizing when this is the right approach, because they can look awfully similar. An example of this is graph searching, e.g. BFS or Dijkstra's algorithm. The typical implementation is a function. But if you make Dijkstra a class, with (say) a function to iterate through nodes, it lets you do several things that would be difficult wit…

None of these situations require an object to do. You can always have a function that takes in an extra ‘state’ argument. You can then do everything you said by passing in the corresponding state values.

You're talking about s.f(x) vs f(s,x)?

Re: The use of `class` for things that should be simple free functions

#62

Post by endgame »

amw-zero wrote: post #48
dataflow wrote: post #18

Counter-point: while in many situations this isn't the right approach, it's worth recognizing when this is the right approach, because they can look awfully similar. An example of this is graph searching, e.g. BFS or Dijkstra's algorithm. The typical implementation is a function. But if you make Dijkstra a class, with (say) a function to iterate through nodes, it lets you do several things that would be difficult wit…

None of these situations require an object to do. You can always have a function that takes in an extra ‘state’ argument. You can then do everything you said by passing in the corresponding state values.

Can't you close over the state, so the library doesn't need to see and pass around the extra parameters?

Re: The use of `class` for things that should be simple free functions

#64

Post by hamandcheese »

amw-zero wrote: post #54
cataphract wrote: post #51

Earlier quoted context omitted.

But if you're passing a state object around, you might as well use a class, no? Admittedly simplifying a bit, an instance method is a function that implicitly takes "this" as the first argument.

Why? You would never suggest this if OO wasn’t the predominant paradigm. What is the benefit of implicitly passing the parameter? I prefer to see it passed explicitly, so the implicit passing is a downside to me, not a benefit.

The benefit is encapsulation.

Re: The use of `class` for things that should be simple free functions

#65

Post by fauigerzigerk »

amw-zero wrote: post #54
cataphract wrote: post #51

Earlier quoted context omitted.

But if you're passing a state object around, you might as well use a class, no? Admittedly simplifying a bit, an instance method is a function that implicitly takes "this" as the first argument.

Why? You would never suggest this if OO wasn’t the predominant paradigm. What is the benefit of implicitly passing the parameter? I prefer to see it passed explicitly, so the implicit passing is a downside to me, not a benefit.

The canonical answer is encapsulation. But in my view it's rarely a good idea to couple state related to an algorithm's invocation (e.g a cache) with the data structure itself.

Re: The use of `class` for things that should be simple free functions

#67

Post by jerome-jh »

To me the original sin of the example is not to perform the calculation in the constructor. The third version, the one with the "int count() const" method and without the h and w members, is perfectly valid and (correct me if I'm wrong) thread-safe. It is a bit longer than the 'functional' implementation but does handle memoization. This is basically the C++ way to make a 'closure'.

The point is certainly valid, but the example could have been more carefully chosen.

Re: The use of `class` for things that should be simple free functions

#70

Post by jabirali »

amw-zero wrote: post #54
cataphract wrote: post #51

Earlier quoted context omitted.

But if you're passing a state object around, you might as well use a class, no? Admittedly simplifying a bit, an instance method is a function that implicitly takes "this" as the first argument.

Why? You would never suggest this if OO wasn’t the predominant paradigm. What is the benefit of implicitly passing the parameter? I prefer to see it passed explicitly, so the implicit passing is a downside to me, not a benefit.

In many languages, it is an explicit parameter though.

For instance, in Python, one would define a function with `def fun(state)` or a class method with `def fun(self)`. In the function body, one would use respectively `state.var` or `self.var` to refer to a variable `var` in the state object. Running it is then done using `fun(state)` or `state.fun()`.

There are some minor syntactic differences between the two, but I find both these examples to be just as explicit...

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