Philosophy of Computer Science: Online Resources

Errata

1. p. xix, last line:
   "LaTex" should be:    LaTeX

   (or, even better: L^AT_EX)

2. p. 6, Further Reading box, last line of paragraph 1:
   "17." should be:    17.)

3. p. 84, Figure 4.1:
   Line T should have boldface lines only in those locations where line O has gaps (instead of line T being a continuous boldface line).

   (The idea is that the boldface portions represent the hypotheses and the non-boldface portions represent the observations.)

4. p. 92, 2nd full paragraph:
   The opening sentence of this paragraph seems to me to be a bit confusing. To see why, link to the Further Readings for this section.

5. p. 92, 2nd full paragraph, line 2:
   "(GOFAI) Haugeland, 1985);" should be:    (GOFAI); Haugeland, 1985),

   (with a semicolon before "Haugeland" and a comma after the date)

6. p. 120, Figure 7.1, should have appeared on p. 119 as the fourth epigraph (after the one by Min).

7. p. 138, §7.4.3.3:
   There are four "optional, additional instructions": halt, exit, abstraction, and recursion.

   Therefore, on line 8, "Abstraction" should be left-justified under "An "exit" instruction", and only its text beginning with "A structured programming language" and ending with the citation to Liskov and Zilles should be a displayed quotation.

8. p. 152, §7.7.1:
   1. There is an error only in the ePub version of the book (the printed version and the PDF version are correct):

      In the ePub version, there are two occurrences of algorithm A^2*_H.

      The first one is incorrect; it should be:

      algorithm A^1*_H(C,i):
      begin
        if C(i)↓
        then output 'halts'
        else output 'loops'
      end.

      (Thanks to Chen Yiwen for pointing this out.)

   2. The formula for H is missing some left angle brackets. It should read as follows:
      H = {⟨⟨C₁, i₁⟩, "halts"⟩, … , ⟨⟨C_j, i_k⟩ "loops"⟩, …}

9. p. 154, §7.7.2, Step 4:
   As I note in footnote 39, my notation in this section is "rather informal". But, as Stefanos Baziotis pointed out to me, it cam also be confusing. In particular (and here I quote from Baziotis's email):
   A*_H takes two inputs, not one. In other words, structurally it looks like A*_H(A, b). But A takes two inputs, so asking whether A will, or will not halt on b (which is what is implied by passing both as input to A*_H) doesn't seem to make sense because A needs more than b as input.

   It seems that what you want is a definition of A*_H that gets one input and passes it as both C and i to A_H. Something like this (yes, for better or worse I use a Pythonic style because it seems simple):

   def A_H(C, i):
     if C halts on i:
       return True
     else:
       return False

   def A*_H(C):
     if A_H(C, C):
       while True:
         pass
     else:
       print("loops")

   Now take A*_H(A*_H):

   1. If A*_H halts on A*_H, then A*_H(A*_H) loops
   2. If A*_H loops on A*_H, then A*_H(A*_H) outputs "loops" and halts (by the way, contrary to the text in the book, I think it first outputs "loops" and then it halts)

   Now you can use the original argument:

   If A*_H halts on A*_H, then, by (1), A*_H(A*_H) loops, i.e., A*_H on A*_H loops. That already is a contradiction, so we take the alternative case. If A*_H loops on A*_H, then, by (2), A*_H(A*_H) halts, i.e., A*_H on A*_H halts, which is again a contradiction. In both cases, we have a contradiction.

10. Ch. 7 endnotes in the ePub version have a numbering problem:
    There are two endnotes numbered 16. In the body of the text, endnote number 17 points to the second of the ones numbered 16, so the numbering from 16–29 are all off by one numeral.

    To make matters worse, endnotes 30 and 31 are reversed in the listing at the end of the chapter!

    Please see the printed version for the correct numbering of endnotes for this chapter! (Readers of the ePub version who do not have access to the printed version may contact me for a correct version of Ch. 7.)

    (Thanks to Chen Yiwen for pointing this out.)

11. p. 160, §8.5.1:
    The opening passage, "In §§9, 10 … my italics", should be a displayed quotation.

12. p. 193, Digression on Notation, paragraph 5, line 1:
    "∂" should be:    ə

13. p. 216:
    The entire passage beginning with "But this has two consequences …" and ending with the citation to Searle 1990 should be a displayed quotation.

14. p. 412, §18.3.3, paragraph 1, lines 3–4:
    The URL for the Internet-dog cartoon should be enclosed in parentheses.

15. p. 419, §18.6, paragraph 0, line 4;
    p. 422, §18.7.2, paragraph 2, line 2:
    "natural-language-understanding" should be: natural-language-processing.
    • See the Further Readings for Chapter 18 for an explanation.

16. p. 432, third Dennett quotation, line 3:
    "p. 100061" should be: p. 10061

17. p. 489, bibliography entry for Simon 1962:
    "1996a" should be: 1996b

18. p. 504, Index:
    The entry for "Post productions" should include a few more pages:
    Post productions 113, 140, 240, 276

19. p. 505, Index:
    The single entry "Scott, Peter 342, 347, 402" should be two separate entries:
    Scott, Dana 342, 347
    Scott, Peter 402