Quoting a footnote of SICP, the book I'm reading: (emphasis mine)

9. Since nested applications of car and cdr are cumbersome to write, Lisp dialects provide abbreviations for them -- for instance,

(cadr (arg)) = (car (cdr (arg)))

The names of all such procedures start with c and end with r. Each a between them stands for a car operation and each d for a cdr operation, to be applied in the same order in which they appear in the name. The names car and cdr persist because simple combinations like cadr are pronounceable.

Background information: car and cdr are primitive procedures in a programming language called "Lisp". In Lisp dialects (i.e. variants), cadr is a shorthand for successive applications of them.

Actually I have two question here:

  1. How to pronounce simple combinations like cadr?
  2. Why do the names car and cdr persist? I cannot see the relationship between the pronounceability of cadr and the reservation of car and cdr.

closed as off-topic by Nathan Tuggy, Glorfindel, Rompey, Brian Tompsett - 汤莱恩, shin Jan 19 '17 at 12:36

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    I'm voting to close this question as off-topic because it's about programming culture, not English in general, and we can't guarantee good voting on answers. – Nathan Tuggy Jan 19 '17 at 9:36
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    (I'm actually a programmer myself, although I've never done much with Lisp or Scheme, and while I could probably vote well enough myself, I can't say the same for most ELLers, and there's no reason to suppose they could.) – Nathan Tuggy Jan 19 '17 at 9:37

According to COMMON LISP: A Gentle Introduction to Symbolic Computation (by David S. Touretzky):

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As to pronunciation - that's more ambiguous question. The functions are all acronyms (for example, CAR stands for Contents of Address portion of Register, and CDR stands for Contents of Decrement portion of Register), so why is this acronym pronounced this way often comes down to how the sounds of the letters roll together. But I can certainly see the links between CAR/CDR and their derivatives.

From here on in I'm guessing, but from what I can see:

CAR breaks down to C (k) - AR (ar) CDR breaks down to C (cou) - DR (der)

...and the combinations of CA, CD, AR and DR more or less work pronunciation-wise from there on in, with additional A's and D's are tacked on accordingly.

Why CADR is pronounced kae-der and not ka-der, presumably it's to differentiate it from CADAR, which would have a very similar (and easily confused) pronunciation (ka-dar) otherwise.

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