<p>Mathematica uses symbolic manipulation of expressions combined with significance arithmetic, so numeric resolution can fail, and then the user is left holding the error as a result. However, similarly to how the Constructive Real system has syntax trees, the exception handler can have access to the unresolved symbolic expression, which he could perform more computation with if he knew what to do with it. This is interesting.</p>
- <p>There is a first edition of this book. The same concepts are described in those pages, but the story is not as well told, and no one has come full circle to say it made any sense to them. Well, one colleague, after reviewing the first edition, admitted he was bewildered by it and asked if I was proposing that we build Turing Machines. After all we are the music makers, in the music business, so to speak; only instead of being written in notes, our music is written in transistors and layout. So then, he rightfully asks, what is the proposal here? I can only point him at Mitch Alsup's book, and ponder how I can tell this story differently.</p>
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<p>There is a first edition of this book.<RT·endnote>TODO·cite: the first edition, and the Quicklisp release of the Lisp library.</RT·endnote> The same concepts are described in those pages, but the story is not as well told, and no one has come full circle to say that it made sense. One colleague who reviewed it admitted he was bewildered by it, and asked whether I was proposing that we build Turing Machines. After all, we are the music makers,<RT·endnote>Arthur O'Shaughnessy, "Ode", in <em>Music and Moonlight</em> (London: Chatto and Windus, 1874).</RT·endnote>, so to speak; and we write notes in transistors and layout. So then, he rightly asked, "What is the proposal here?" I have yet to give him an answer. Perhaps this second edition will help.</p>
<p>There is no hardware specification for a new proposed commercial machine in this book. This book is not proposing to build in hardware a Turing Machine. This is an absolute. Building a RT machine might be interesting. It is true that the organization for it is described in this book. Yet this is certainly not the proposal here. Rather this book explains and justifies a set of features that are planned to be incorporated into a commercial machine, one which I proposed to model and build in 2005. There was some interest, but ultimately we did not raise money for it.</p>