Name: CS50 2018 - リーディング4 - データ構造 (CS50 2018 - Lecture 4 - Data Structures)
Uploaded: 2021-01-14T07:57:06.000Z
Duration: 2 h 3 min 28 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

DAVID J. MALAN: All right, this is CS50 and this is a lecture four.

So we're here in beautiful Lowell Lecture Hall

And we're joined by some friends that will soon

But before then, recall that last time we took a look at CS50 IDE.

This was a new web-based programming environment similar in spirit

to CS50 Sandbox and CS50 Lab, but added a few features.

For instance, what features did it add to you--

So debug50, which opens that side panel that

allows you to step through your code, step by step, and see variables.

DAVID J. MALAN: Check50 as well, which is a CS50 specific tool that

allows you to check the correctness of your code

much like the teaching fellows would when providing feedback on it.

Running a series of tests that pretty much are

the same tests that a lot of the homework's

will encourage you yourself to run manually,

There's a little hidden Easter egg that we don't use this semester,

If you look for a small puzzle piece, you

can actually convert your C code back to Scratch like puzzle pieces

and back and forth, and back to forth, thanks to Kareem and some of the team.

So that is there, but by now, it's probably better

So there's a couple of our other tools that we've

used over time of course besides check50 and debug50.

We've of course used printf and when is printf useful?

Like when might you want to use it beyond needing to just print something

DAVID J. MALAN: Yeah, so to find where your bug is.

If you just, kind of, want to print out variables, value or some kind of text

so you know what's going on and you don't necessarily

AUDIENCE: If you have a long formula for something [INAUDIBLE]

AUDIENCE: How running-- like going through debug50 50 times.

Well, in real life-- so you might want to use printf

when you have maybe a nested loop, and you want to put a printf inside loop

Of course, you could use debug50, but you

might end up running debug50 or clicking next, next, next, next, next, next,

next so many times that gets a little tedious.

But do keep in mind, you can just put a breakpoint deeper into your code

as well and perhaps remove an earlier breakpoint as well.

And honestly, all the time, whether it's in C or other languages,

do I find myself occasionally using printf just to type out printf in here

just so that I can literally see if my code got to a certain point in here

But the debugger you're going to find now

and hence forth so much more powerful, so much more versatile.

So if you haven't already gotten to the habit of using debug50 by all

means start and use those breakpoints to actually walk through your code

So style50, of course, checks the style of your code much like the teaching

fellows might, and it shows you in red or green

what spaces you might want to delete, what spaces you might

So it's more readable for you and others.

When should you instinctively reach for help50?

AUDIENCE: When you don't understand an error message.

Yeah, when you don't understand an error message.

It doesn't really quite work and you're seeing a cryptic error message.

Eventually, you'll get the muscle memory and the sort of exposure

to just know, oh, I remember what that means.

But until then, run help50 at the beginning of that same command,

and it's going to try to detect what your error is

and provide TF-like feedback on how to actually work around that.

You'll see two on the course's website is a wonderful handout made

by Emily Hong, one of our own teaching fellows,

that introduces all of these tools, and a few more,

and gets you into the habit of thinking about things.

If I have this problem, then do this or else

if I have this problem do this other thing.

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CS50 2018 - リーディング4 - データ構造 (CS50 2018 - Lecture 4 - Data Structures)

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