Lecture 4 | Programming Paradigms (Stanford)

[@Abdullah-mg5zl]

Great professor! A very good lecturer. I like how he pauses, waits for people to digest, asks if they understand, answers questions, then moves on. Also the way he explains things is superb. He uses clear and consise explanations yet they are not too jammed packed to make them hard to understand.

[@alhaithamaljabri6126]

Abdullah, Nice channel bruh!

[@UberOcelot]

This guy is incredible, seriously maybe the best CS lecturer I've seen.

[@frankie_goestohollywood]

Really!!! I could watch him for hours even if I don't understand everything he is saying :-) Fantastic Professor.

[@paulchen355]

agreed !

[@lucasroncatobatista995]

This professor is awesome! He explains how C manages memory in a very graphical and easy to understand way. He demystify pointer once forever...

[@antonehmac]

Yeah, it seems to be a question that all teachers need to ask, and yet is difficult to frame well. You don't want to leave anyone behind but calling attention to something someone has missed is sensitive for both the student and the teacher, who may feel judged for remedial need or lack of clarity respectively. I think he handles it well, and the moment that became awkward appeared to be when he could tell a student wasn't following and he was urging that student to ask for the needed clarity.

[@jaggis4914]

I taught myself C. Thanks to Jerry!

[@ehteramuddinmohammed3995]

What a wonderful lecture!!! I like the way he teaches, the way he puts it down on board to make students visualise the happenings in the memory. Thank you for such a great explanation.

[@timhawthorn7903]

Thanks Jerry, this is exactly what I wanted to know. I feel like I'm finally understanding what goes on under the bonnet.

[@PaulKruskamp]

It helps to be sitting next to a compiler while watching this.

[@dimashur]

the last two lectures were so informative, i love this serious of lectures

[@jtetrfs5367]

The compiler won't do pointer arithmetic on void* pointers. So you want to trick the compiler into doing pointer arithmetic by casting to...something! So why char*? Because it is one byte in size. You could have also cast to int*, but then, since sizeof(int) = 4 * sizeof(char), you would need to do (i * elemSize) / 4. In other words, casting to char* gives you the simplest expression (and the most efficient, too).

[@infinitesimotel]

really excellent lecturer and progression.

[@AronNimzo]

I think it is better to call this swap function in follwing way: int main(void) { float x, y; swap(&x, &y, sizeof(x)); return 0; } As long as x and y have the same type it will work.

[@AnkurSharma-je1ro]

We can check a pre condition in calling routine assert(sizeof(x) == sizeof(y))

[@shanashinigami]

Really great stuff, we're lucky to get access to such a stellar lecture

[@maengu2]

Thank you for the great and clear lecture!

[@shobhitverma2478]

I'm going to share timestamps for whole video so that it'll be helpful for someone to save time. 23:37 - swapping two strings using generic swap function. 35:02 - writing generic linear search function.

[@PixelPulse168]

Finally, I can understand the working principle of Pointer!!!!

[@briane5467]

#include double main (is that clear) {

[@chelvan2]

it should be for(int i = 0; i < n; i++) .. and n should be declare before.. by something

[@Jurily]

@3dfabio "After a long and arduous process, the standard was completed in 1989 and ratified as ANSI X3.159-1989 "Programming Language C." This version of the language is often referred to as "ANSI C", or sometimes "C89" (to distinguish it from C99)."

[@MarcusAseth]

I'll call my son People and send him to Stanford so that this great professor will make sure that this stuff make sense to him :D

[@efeakn4672]

ı tried that 30.00 Fred Wilma swap thing without the & it still made the swap :/

[@alexpark-q8m]

great lecture ever

[@loganrathbone3856]

int main(void) { if ( !does_that_make_sense_to_people() ) professor_explodes(); return 0; }

[@Moosorkh]

esle{ professor = gets-happy(); print(professor); }

[@steffens.1734]

@@franciscodeaguirre1754 C and Python, both have there advanteges and disadvanteges. With more progress in your learning you wouldn't repeat your comment.

[@shadyganem5448]

int main(void) { if ( !does_that_make_sense(&people) ) professor_explodes(); return 0; }

[@ch3ragCS]

Still learning in 2017

[@ValeriCFBG]

you could make generic swap to work for int and short by first casting the short to int

[@anguruso]

These are really great examples. Except some of the naughty behaviour is being clamped down by my compiler. I'm using whatever C compiler comes with VS2010

[@jeyosman1]

which book do recommand me to read about memory like this class now

[@thedylan123456789]

try using MinW32 and GCC or cygwin and GCC

[@matthewsmeets]

It's a good idea that these lectures were recorded, even from home at 75% speed I cannot keep up with making notes.

[@Martin1456215]

At 43:30 he is using a "hack". He casts base to char* and he mentions that it is also possible to use an unsigned long* instead of char*. Why is it possible to use unsigned long*? Unsigned long is a 4 byte datatype, char 1 byte.

[@platcrab4890]

Martin Ennemoser char is also 4

[@dragosborosgpt]

quite clear, thanks

[@firefokos]

This is great thank you

[@lekimsey]

good teaching.

[@alibabascience9406]

how a void *lsearch return elemAddr ? Professor, thank you is verry hard explication

[@jamesedmonds6814]

most people have either 32 bit or 64 bit systems, if you watched his first video he says to assume a int is 4 bytes and a long is 8 while a char is 2. He did say it was system specific. Your like jumping into a middle of a conversation spouting out stuff trying to sound smart. Listen from the start then you should feel stupid.

[@platcrab4890]

James Edmonds I'm pretty sure a char is 4 bytes

[@oneplusonetwo]

43:00 i dont understand why pointer type has anything to do with pointer arithmetic, the compiler should always know the what hardware it is running on, so it should always know the size of mem address, like 32bit or 64bit. so for example, compiler running on 32 bit system, then "base" should contain a 32bits long data(address of void *base), and "i" and "elemSize" are both int(also 32 bits long), so why compiler don't know how to interpret? or why compiler don't do void * pointer arithmetic?

[@yoyuepz]

@dimipeli yea i think this as well.. and being from stanford they wouldnt make as many mistakes as other "normal" univerisites? Maybe i am wrong? But i do like this teacher! :)

[@irock9114]

can somebody explain what he did with that char* hack (at 43:30)? :S tried that piece of code on searching a 10 element integer array.. it worked fine with (char*) and (short*) casts. but the program crashed when i used (int*) and (unsigned long*).

[@Arunsharma-tf5xp]

Why he hadn't use "*" inside that void swap function in as memcopy(*vp1, *vp1, size) because writing just vp1 return it's address not it's value that it is actually pointing 🙄

[@aayushchhabra7465]

That is due to the specification of memcpy function. memcpy explicitly expects you to pass the locations of destination and source without dereferencing it.

[@bobesfanchi]

You can't derefrence a void pointer. C++ needs to know the size of the pointer to be able to deref it.

[@DeBaimbo]

Is there a book that treats exactly these subjects? I like listening to this professor, but I feel more comfortable studying on a book.

[@AnkurSharma-je1ro]

Computer science: A Programmer's perspective

[@DeBaimbo]

@@AnkurSharma-je1ro Thanks!

[@linosnoto]

where can i find the assignments

[@danielgray8053]

did you find them?

[@ncmathsadist]

the bad swap near 51:00 gave me a "bus error 10."

[@666friends]

@NameNotaNumber A good programmer knows at least one language from the different programming types.

[@Kikeron]

He says afterwards "It’s incidentally normal math with char *s because characters are 1-byte wide, so the scaling factor is just 1, okay?"

[@bishalthapa4639]

That's heavy :)

[@SuperGanga2010]

@dimipeli Yeah, he does. But sometimes students' questions aren't well-formed and understandable, so as soon as the lecture is being filmed, he has no time for such things. Would you like to see how he tries to understand students' questions for 1 minute or so instead of telling new information? I wouldn't.

[@jakefund6728]

Trying to run project 2 - Segmentation fault =(

[@ductran5913]

I got seg fault 11 when run imdb-test. Any one help please :)

[@flyaloy1]

this happens when you try to access to a memory reference that doesn't belong to your program, maybe your pointer is out of range of something like that.

[@matthewsmeets]

@@flyaloy1 Correct, try allocating some random local variables around your code so you have a bigger heap to work with.

[@jamesedmonds6814]

he says it in the video more than once.

[@YoungYSL]

Well I can't understand why audience is so dissatisfied. I don't know wether it is normal in USA, maybe cause I am from Ukraine. Here we have absolutely different type of interaction between class and lecturer. P.S. Lecturer does his work in a great way, really miss such lecturers in UA

[@aajr95]

thats because its over all of their heads

[@invalidacess]

lol so true lol... i notice that the views keep getting smaller and smaller as u go from lecture 1 - 4 lol wonder y?

[@AnkurSharma-je1ro]

Thats is surfing vs following

[@Grundalizer]

I do not get programming at all.

[@rhshriva]

bible of C

[@dimipeli]

He makes some mistakes here and there, and misinterprets some of the students' questions, but he is still a good lecturer.

[@rrook88]

look like beggining of mem fragmentation.. solution. buy defrag software

[@acho8387]

Am I the only one getting super distracted by this "does that make sense" every other sentence? It really breaks my focus..

[@yeors]

make sense?? XD jajajajajajajajaja

[@ZainaWalkingTheLine]

Hahahahha wt language is that?!! :$

[@Maisonier]

english