APL study session 2

Discussion of the second study group can go here! APL Overview

[ <<< session 1 | session 3 >>>]

This is a wiki post - feel free to edit to add links from the lesson or other useful info.

Overview

  • Basic math operators (continued)
    • Divide sign: reciprocal (monadic); divided by (dyadic)
    • Times sign: direction; times
      • Magnitude and direction of complex numbers; the unit circle
    • Star: exponential; power
      • Compound interest and exponential functions
      • Limits
      • Euler’s identity
  • Precedence

Study session resources

Video timeline - thank you @Daniel

00:00 APL: a hintsight of a brilliant plan

04:18 Get ready to continue our APL learning

07:44 times sign backtick - and review of how to get bookmark of APL keyboard for Jupyter notebook

09:32 See how (Dyadic x) times work and how (monadic x) direction work with real numbers

12:20 How does (monadic x) direction work with complex number

16:26 Keyboard preferences

18:53 What is complex number in complex plane?

22:24 what is 2 + 2i written in APL? 2j2? What does direction do? What is a unit circle? How to understand the direction of a complex number in terms of a unit circle

Images

29:51 Learn magnitude

34:34 Learn divide sign

35:09 How to understand reciprocal in APL?

Images

36:48 clean up the notebook

38:16 Precedence

44:04 learn power sign *: how does (monadic *) exponential work? how does (dyadic *) power work?

46:38 What is e? How did Jeremy explain it step by step?

Images

53:07 What kids’ reaction to Jeremy’s explanations of e, limit and infinity? How do we understand of e?

55:14 Who is e named after? Wha are the interesting/crazy things about e?

56:55 How to get e in APL? How to use power (Dyadic)?

57:59 More discussion of the interpretation of eiπ+1=0 in terms of rotating on the unit circle

1:00:31 How to display the operation precedence in APL?

Images

5 Likes

Thanks Jeremy! Could you please make this a wiki topic?

Done.

1 Like

Going to have to absent myself from the live sessions. I tried making the 2am time work but is proving to be unsustainable to wake up in the middle of my night sleep to do that! Will be following the videos for sure, as with the other walkthrough. Thanks for hosting these, Jeremy.

9 Likes

We’ll miss you - but glad you’re looking after yourself

Same here Alex. I really loved joining one of the live walk through sessions, was more fun since it felt more conversational, but 2am is literally the last hour that I allow myself to still stay awake these days. I’ll be catching up on the recordings as well.

1 Like

Here is a link to the 3Blue1Brown video mentioned when discussing Euler’s identity

9 Likes

It’s 0530 hrs for me. Haven’t woken up at that time, ever. :sleepy:

I plan to catch up to the recordings as well.

A brief note of apl study group 2

00:00 APL: a hintsight of a brilliant plan

04:18 Get ready to continue our APL learning

07:44 times sign backtick - and review of how to get bookmark of APL keyboard for Jupyter notebook

09:32 See how (Dyadic x) times work and how (monadic x) direction work with real numbers

12:20 How does (monadic x) direction work with complex number

16:26 Keyboard preferences

18:53 What is complex number in complex plane?

22:24 what is 2 + 2i written in APL? 2j2? What does direction do? What is a unit circle? How to understand the direction of a complex number in terms of a unit circle

Images

29:51 Learn magnitude

34:34 Learn divide sign

35:09 How to understand reciprocal in APL?

Images

36:48 clean up the notebook

38:16 Precedence

44:04 learn power sign *: how does (monadic *) exponential work? how does (dyadic *) power work?

46:38 What is e? How did Jeremy explain it step by step?

Images

53:07 What kids’ reaction to Jeremy’s explanations of e, limit and infinity? How do we understand of e?

55:14 Who is e named after? Wha are the interesting/crazy things about e?

56:55 How to get e in APL? How to use power (Dyadic)?

57:59 More discussion of the interpretation of e^{i\pi} + 1 = 0 in terms of rotating on the unit circle

1:00:31 How to display the operation precedence in APL?

Images

precedence-order

3 Likes

Suuuper helpful @Daniel! Could be great to edit the first post and add a link to this one?

Also if anyone creates a trimmed down version for youtube timestamps, please let me know and I’ll put them into the youtube description. (Or add them as a comment on youtube itself).

1 Like

What do you mean by “trimmed down”? What’s the ideal format for YouTube?

Here’s an example: Live coding 1 - YouTube

If you look at the description (click “see more”) you can see hyperlinked timestamps. The links appear automatically when the text is in that format. As well as the convenient links in the description, you also get chapter markers automatically that look like this:

Basically, you want markers around when each new thought/section starts, and they should be short enough that they make sense as chapter titles. Generally not more than 5-6 words if possible.

Normally I just start with @Daniel’s notes, delete the ones that don’t really seem like a major new section, and trim down the rest to a short summary of what it’s about. I’m not doing it for the APL study groups since I’m a bit overwhelmed with other stuff right now.

1 Like