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Classes vs. Data Structures

blog.cleancoder.com

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Re: Classes vs. Data Structures

#61

Post by bendbro »

ivan_gammel wrote: post #60
bendbro wrote: post #56

Earlier quoted context omitted.

Ah, and what owns these functions? And more pressingly, why would you ever pass a data structure to a function that had more than one algorithm to compute a result? The data structure (or perhaps some intermediary (an adapter?)) should own the algorithm within a function that computes only on that data structure. This ensures that all methods associated with your data structure are obviously and explicitly associated…

Did you ever write a program on C? In procedural languages functions are either global or, sometimes, encapsulated in namespaces or modules. Data structures come from that world and do not encapsulate any behavior. In object-oriented languages like Java data structures simply do not exist and are usually emulated via anemic models.

Ah, thanks, that makes perfect sense.

Re: Classes vs. Data Structures

#62

Post by tomrod »

ci5er wrote: post #59
thom wrote: post #39

Earlier quoted context omitted.

The only thing more annoying is when people ape Why's (Poignant) Guide to Ruby and you have to follow the adventures of some tedious otter as it meets the rabbit people who ultimately explain pointers in a way which takes a thousand too many words.

Have you ever come across anything that explains why pointers are hard for some people? I find it difficult to explain pointers to people because I don't understand what they are missing. I could use some help understanding their lack of understanding. When they don't get "indirect reference to the address of a data structure or object in memory", I'm stuck on how to proceed. Pointing people to the very elegant treat…

I don't think I understand pointers. Maybe we can help each other. My mental model of pointers is a map: lat/long identify the object of interest (the local coffee shop), but not what is interesting about it (their menu and hours).

Re: Classes vs. Data Structures

#63

Post by narag »

Jach wrote: post #43
methodover wrote: post #18

Earlier quoted context omitted.

Ding ding ding. The entire article hangs on “imply”. The question of where data is stored for an object is far less important than how to access data in a data structure. Like, the whole reason the data structure is designed the way it is, is to access it in particular ways.

Part of this reminds me of discussing the differences between "data structure" and "algorithm". Sometimes it's hard to separate them, especially since many algorithms don't need anything more elaborate than "get" and "put" into some opaque data store. Add requirements on the data store that make it less opaque (can't "put" for instance, making it immutable) and your algorithms change. Change your algorithms and you m…

Careful. The author is not using "data structure" with the standard Computer Science meaning, but as C language struct. Standard data structures were actually the equivalent to current classes and were associated with a set of functions.

If you bother to take a look to C APIs, you'll find the familiar "handle" parameter, equivalent to the "this" or "self" of OO languages. Setting aside all the philosophical mumbo jumbo, OO is syntactic sugar over those interfaces.

Re: Classes vs. Data Structures

#65

Post by kljhsdfkhjdf »

stupidcar wrote: post #35

Whenever I hear "Socratic dialog", I reach for my revolver. Is there any other form of teaching so irritating and patronising? You might have a brilliant store of insight to impart, but if you insist on trying to do so via a twee, affected and unbelievable conversation with a Mary Sue wise professor, I'm going to write you off as insufferable before the fawning moron you have as proxy for your audience utters their f…

It's really difficult to read. I was actually interested in the author's opinion, but the writing style is far too tedious.

Re: Classes vs. Data Structures

#66

Post by jdmichal »

tomrod wrote: post #62
ci5er wrote: post #59

Earlier quoted context omitted.

Have you ever come across anything that explains why pointers are hard for some people? I find it difficult to explain pointers to people because I don't understand what they are missing. I could use some help understanding their lack of understanding. When they don't get "indirect reference to the address of a data structure or object in memory", I'm stuck on how to proceed. Pointing people to the very elegant treat…

I don't think I understand pointers. Maybe we can help each other. My mental model of pointers is a map: lat/long identify the object of interest (the local coffee shop), but not what is interesting about it (their menu and hours).

To use that analogy: The coordinates tell you where the restaurant is (pointer), but you still have to go to the actual restaurant to get some food (data).

Re: Classes vs. Data Structures

#67

Post by ci5er »

tomrod wrote: post #62
ci5er wrote: post #59

Earlier quoted context omitted.

Have you ever come across anything that explains why pointers are hard for some people? I find it difficult to explain pointers to people because I don't understand what they are missing. I could use some help understanding their lack of understanding. When they don't get "indirect reference to the address of a data structure or object in memory", I'm stuck on how to proceed. Pointing people to the very elegant treat…

I don't think I understand pointers. Maybe we can help each other. My mental model of pointers is a map: lat/long identify the object of interest (the local coffee shop), but not what is interesting about it (their menu and hours).

Hmmm. Interesting. I'm going to have to roll that around in my brain for a day-or-so to see if I can make that compute for me. (Which means I may be back here in a day to check back in!)

Maybe it's because I started in assembly language, but to me, data exists at an address in memory. Or starting at an address in memory. That data might be on integer, a float, a character, the beginning of a string, the head of an object/data-struct, OR an address of data somewhere else (which may be any of the above again). Pointers, to me, are simply an address of an address of a data thingie.

Why would you want to use these? One reason is that pushing large data-objects back-and-forth across function calls is expensive (pointers are usually just 32-bit or 64-bit numbers). Another is that one can have a pool of resources (think polygons in a large 3d scene), that are marked "used" or "unused". This gets a large performance boost from not having to do the whole malloc/free thing on lots and lots of small objects. Another (this is related to the first), the function can receive a data-structure, and modify it (side effects!) without having to copy it and pass the modified copy back.

I'm intrigued by your mental model. Having not thought it through - it seems as if lat/long is appropriate, but maybe even the idea that it is a coffee shop that you will find there is undetermined. (That is: the fact that it is a coffee shop is one of the things that is interesting about it, like the menu and hours. Again, I need to think this through).

Thanks!

Re: Classes vs. Data Structures

#68

Post by andrepd »

stupidcar wrote: post #35

Whenever I hear "Socratic dialog", I reach for my revolver. Is there any other form of teaching so irritating and patronising? You might have a brilliant store of insight to impart, but if you insist on trying to do so via a twee, affected and unbelievable conversation with a Mary Sue wise professor, I'm going to write you off as insufferable before the fawning moron you have as proxy for your audience utters their f…

Ironically, this comment in turn reeks of arrogance itself. Why so aggressive, we get it doesn't work for you you but maybe it suits other people?

Re: Classes vs. Data Structures

#69

Post by devnonymous »

tomrod wrote: post #62
ci5er wrote: post #59

Earlier quoted context omitted.

Have you ever come across anything that explains why pointers are hard for some people? I find it difficult to explain pointers to people because I don't understand what they are missing. I could use some help understanding their lack of understanding. When they don't get "indirect reference to the address of a data structure or object in memory", I'm stuck on how to proceed. Pointing people to the very elegant treat…

I don't think I understand pointers. Maybe we can help each other. My mental model of pointers is a map: lat/long identify the object of interest (the local coffee shop), but not what is interesting about it (their menu and hours).

Hmm, your mental model possibly could use a tweak. Yes, a pointer is like a map. It tells you how to get to the thing but it isn't the thing. It is a reference point, a pointer to the thing. The thing that it points to might be a library, a museum or a place to pick up more maps. Irrespective, the thing to remember is it something to takes you there it is not the place.

You may also pass around the map to your friend in effect showing them how to get to the place, without possibly even having seen the place yourself.

And if you are a bad person, you could share maps that lead to dead end dumps

Re: Classes vs. Data Structures

#70

Post by ValleyOfTheMtns »

stupidcar wrote: post #35

Whenever I hear "Socratic dialog", I reach for my revolver. Is there any other form of teaching so irritating and patronising? You might have a brilliant store of insight to impart, but if you insist on trying to do so via a twee, affected and unbelievable conversation with a Mary Sue wise professor, I'm going to write you off as insufferable before the fawning moron you have as proxy for your audience utters their f…

I got a few lines down and couldn't keep going. It's such an irritating way of making an argument.
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