A Philosophy of Software Design

[Forum User]

On Sunday, 24 May 2026 at 01:39:48 UTC, Walter Bright wrote:
> For example, the title of Chapter 10 is "Define Errors out of 
> Existence".

I used Claude Haiku 4.5 for a confirmation that this chapter 
covers
the design of an unset function. There is also a talk of 
Outsterhout
on YT which covers this topic. [0]

This completely made up fragment of code

    unset ("x");
    unset ("x");

may be a copy-paste mistake (modify is missing). The author proba-
bly wanted to write

    unset ("x");
    unset ("y");

If the unset is not - as endorsed by Outsterhout - made idempotent
but throwing this error would have been detected as early as when 
the first `make test` is issued.

[0] A Philosophy of Software Design | John Ousterhout | Talks at 
Google
     https://www.youtube.com/watch?v=bmSAYlu0NcY
     starting at 00:21:58