In the diagram, the transition images across the top and down the right are: heads then heads, but the text says “accept state … if we first get a tails, then another tails.”
Also, the use of two images in each Coin in the alphabet is confusing, as a coin has only one face at a time.
Thanks Jim for reading and also for pointing out this issue. You’re right: it should be “heads, heads” in the text. I’ll change it in the next release.
Don’t hesitate to share if you find other questionable things. It’s much appriciated.
Hi Staffan,
Happy to spot things like this. Your book is excellent; I’m really enjoying it.
I had another one, more a refinement than an error. I’ve been a programmer for 50+ years, so I was around when ASCII was invented. Your description of the “pillow” character on page 34 (of the PDF) is not precise. ASCII is generally considered to be 0-127. The “upper” ASCII plane (where the pillow is at 164) is considered “Extended ASCII” as it requires an 8th bit. There were many names for this extended plane over the years, but to call it unqualified ASCII is imprecise and confused me at first. I’m sensitive to confusion, because if it confuses me, it’ll confuse others. A better way to describe it would be as Extended ASCII, or even better, as Unicode, where it was introduced in 1993.
But honestly, as writers and editors like to say, “kill your darlings.” You could throw this side note away; it has only minor historical curiosity as the currency idea experienced only sporadic adoption, but more importantly, the side note adds nothing to the discussion of the pillow designating the empty set.
Jim
Yes, 7-bit ASCII (and 8-bit extension) deserves a nuanced explanation in the book. I read today that ASCII’s roots can be traced back to telegraph codes, where it was initially used as a 7-bit teleprinter code. The formal development of the ASCII standard began in 1961, and the first edition of the standard was published in 1963, followed by a major revision in 1967 and a final update in 1986.
I remember myself that on early Swedish computers, like the ABC 80, some less-used characters in the standard ASCII table were replaced with the letters Å, Ä, and Ö to accommodate the Swedish alphabet. The “¤” symbol was also included and was, for example, used in ABC BASIC to distinguish string variables from variables of other types.
