Toots for rsc@hachyderm.io account

Written by Russ Cox on 2025-01-13 at 18:36

Does anyone know the effective time limit for GitHub comment edits being included in the comment text that is emailed to issue subscribers?

GitHub renders "- #12345" differently on web (nice link with title and issue status) vs email (literally a useless blue #12345).

I "fix" this by writing an explicit link TITLE HERE #12345, which shows the link number and title in both contexts, but that isn't as nice as the default web display, omits issue status, and so on.

If I could post the explicit link, wait appropriately long, and then edit the comment to use an implicit link, then maybe email would have something useful and web would be even better, at least after the time delay.

But what is the time delay?

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Written by Russ Cox on 2024-12-04 at 14:49

Day 4 part 2 #AdventOfCode

d shift3 m produces the 3 matrices shifted by d*-1 0 1.

d MAS m identifies the A in MAS in direction d.

d xMAS m identifies the A in MAS in direction d or -d.

xMAS m identifies the A in an X-MAS.

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Shared by Russ Cox on 2024-12-04 at 14:45 (original by Russ Cox)

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Written by Russ Cox on 2024-12-04 at 14:45

Day 4 part 1 https://adventofcode.com/2024/day/4 #AdventOfCode

pad dot-pads the matrix to avoid wraparound.

x y shift m rotates the matrix x left, y down.

d(=x y) shift4 m produces the 4 matrices shifted by d*0 1 2 3.

d XMAS m identifies the X in XMAS in direction d.

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Shared by Russ Cox on 2024-12-03 at 19:26 (original by Leon P Smith)

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Written by Russ Cox on 2024-12-03 at 15:05

Well, it's been 2/3 of a year since the xz attack.

Is software safer now?

Serious question.

What improvements have we made?

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Shared by Russ Cox on 2024-12-03 at 06:33 (original by Russ Cox)

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Written by Russ Cox on 2024-12-03 at 06:32

Day 3 part 2.

The function 'c step2 s' is the updated state machine, with an extra value tracking whether mul(x,y) is enabled. step2 takes care of do()/don't() processing and invokes 'step' (from part 1) to handle mul(x,y) when appropriate.

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Written by Russ Cox on 2024-12-03 at 06:31

Day 3 part 1.

The function 'c step s' steps the state machine state s to incorporate the new character c.

(step/ flip x) runs the state machine over the whole string, left to right.

The reduction base case for "...yz" is 'y' step 'z', which step rewrites to ('y' step 'z' step initial-state).

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Written by Russ Cox on 2024-12-02 at 15:35

Day 2:

sample = read "sample.txt"

op delta x = (1 drop x) - -1 drop x

op safeInc x = &/ (delta x) in 1 2 3

op safeDec x = &/ (delta x) in -1 -2 -3

op safe x = (safeInc x) | safeDec x

op solve x = +/ safe@ x

solve sample

op i delete x = (i != iota rho x) sel x

op safe2 x = |/ safe@ (iota rho x) @delete x

op solve2 x = +/ safe2@ x

solve sample

(Using the non-standard map operator-modifier '@' that I added to my copy in 2021. https://github.com/rsc/ivy)

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Written by Russ Cox on 2024-12-02 at 15:34

Ivy remains a good choice for

[#]AdventOfCode.

Day 1:

sample = transp read "sample.txt"

op sort x = x[up x]

op solve x = +/abs (sort x[1]) - sort x[2]

solve sample

op solve2 x = +/x[1] * +/x[1] o.== x[2]

solve2 sample

https://adventofcode.com

(Ivy in 2021: https://www.youtube.com/playlist?list=PLrwpzH1_9ufMLOB6BAdzO08Qx-9jHGfGg)

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Written by Russ Cox on 2024-10-05 at 13:21

SVG, HTML5 Canvas, Apple Core Graphics, PDF, and probably many others all use the same core vector graphics model and operators, which I think of as from PostScript.

Did the creators of PostScript invent these, did they originate in some even earlier system?

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