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Classes vs. Data Structures

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Re: Classes vs. Data Structures

#81

Post by cogman10 »

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).

Do you know what an array is?

If so, then you can think of memory like as a giant array of bytes and a pointer as the index in that array.

Hurray, you now understand pointers :)

Don't muddy it up beyond that.

Re: Classes vs. Data Structures

#82

Post by kasey_junk »

ci5er wrote: post #67
tomrod wrote: post #62

Earlier quoted context omitted.

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 ob…

Note that your model is also an abstraction. Modern architectures move data around between a variety of memory locations (and store it in multiple locations) which are all addressed via the pointer ‘transparently’. It’s not really a memory address anymore and hasn’t been for some time.

That’s not to say your model is bad, it’s the same one I have in my head. But it’s no more ‘real’ than coordinates or library cards or P.O. Box number.

Re: Classes vs. Data Structures

#83

Post by Sebb767 »

charlieflowers wrote: post #34
justinpombrio wrote: post #7

The first set of points: > Classes make functions visible while keeping data implied. Data structures make data visible while keeping functions implied. > Classes make it easy to add types but hard to add functions. Data structures make it easy to add functions but hard to add types. is known as the Expression Problem https://en.wikipedia.org/wiki/Expression_problem . The last point: > Data Structures expose callers…

Regarding the claim ... > Data Structures expose callers to recompilation and redeployment. Classes isolate callers from recompilation and redeployment. ... most projects (maybe all?) I've worked on in 20+ years deployed a full set of new bits upon release, rather than trying to differentiate at the level of which source code files were and were not touched. So this strikes me as a carryover from many years ago when…

In scripted languages you might do an rsync, which only transfers modified data. Or your program could be split into several libraries.

But it seems to be a rather weak point, yes.

Re: Classes vs. Data Structures

#84

Post by narag »

cogman10 wrote: post #78
verall wrote: post #71

Earlier quoted context omitted.

What I see is two types of people, people that understand basic computer architecture and those that don't. The C memory model and pointers come easily to those that understand what a memory address is and how long one is on their favorite architecture. In my experience, people without this knowledge might understand how to use pointers, but not really why they are. And the answer to the "why pointers" question is _n…

Honestly, I think the answer to "Pointers, WTF?" is simply describing how data is stored in memory. This concept is important not only for how pointers work but even how data is stored on a hard drive. You don't have to go into great detail. All you need to do is say this is a number, it takes n number of bytes to store (Most people who haven't been living under a rock have a knowledge of bytes, just explain it to th…

Honestly, I think the answer to "Pointers, WTF?" is simply describing how data is stored in memory.

So is this not how it's explained nowadays? No wonder there's people that doesn't get it. So many concepts, not only about programming, I have learnt in my life first with "this is what happens", then with the precise definition...

Re: Classes vs. Data Structures

#85

Post by ChrisSD »

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).

I'm semi-convinced the reason many people have a problem understanding pointers is because C makes them needlessly confusing. Or at least in my experience people struggle more with C pointers than they do with learning assembly.

Re: Classes vs. Data Structures

#86

Post by narag »

cogman10 wrote: post #81
tomrod wrote: post #62

Earlier quoted context omitted.

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).

Do you know what an array is? If so, then you can think of memory like as a giant array of bytes and a pointer as the index in that array. Hurray, you now understand pointers :) Don't muddy it up beyond that.

Add to that: you store the index in another cell in the array.

Re: Classes vs. Data Structures

#87

Post by CodeMage »

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…

To be fair, actual Socratic dialogue can be very effective and rewarding, without being patronizing. What you're describing there -- what the blog post is like -- that's just as awful as you said, or worse.

I couldn't get much further past this:

What is an object?

    An object is a set of functions that operate upon encapsulated data elements.
...what?

Re: Classes vs. Data Structures

#88

Post by ravenstine »

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…

Yeah, I actually was convinced that it was a great idea and tried to apply it a bunch of times when trying to help teach others. It always worked out really badly.

The Socratic approach can be great when everyone's on the same page, but if you are teaching people from the ground up then all you'll really do is come off as a jerk.

Re: Classes vs. Data Structures

#89

Post by ci5er »

kasey_junk wrote: post #82
ci5er wrote: post #67

Earlier quoted context omitted.

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 ob…

Note that your model is also an abstraction. Modern architectures move data around between a variety of memory locations (and store it in multiple locations) which are all addressed via the pointer ‘transparently’. It’s not really a memory address anymore and hasn’t been for some time. That’s not to say your model is bad, it’s the same one I have in my head. But it’s no more ‘real’ than coordinates or library cards o…

Agreed. But it depends on the computer. On the old vectorized machines like the Cray Y-MP, it was always just a mental model. On even modern embedded systems w/o virtual memory, it's pretty close to being really real.

(I find that the P.O. Box number thing to be a useful general abstraction for me, but it doesn't seem to convey the concept well to people who are confused. Hence the intent behind the intent of my question: "Does anyone know how to effectively teach pointers?")

Re: Classes vs. Data Structures

#90

Post by grawprog »

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 didn't understand pointers until I understood all variables were all a certain size and stored in a specific place in memory. Which I didn't really understand until I'd been programming for a while.
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