eintr: Strange Names
Strange Names
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The name of the ‘cons’ function is not unreasonable: it is an
abbreviation of the word “construct”. The origins of the names for
‘car’ and ‘cdr’, on the other hand, are esoteric: ‘car’ is an acronym
from the phrase “Contents of the Address part of the Register”; and
‘cdr’ (pronounced “could-er”) is an acronym from the phrase “Contents of
the Decrement part of the Register”. These phrases refer to specific
pieces of hardware on the very early computer on which the original Lisp
was developed. Besides being obsolete, the phrases have been completely
irrelevant for more than 25 years to anyone thinking about Lisp.
Nonetheless, although a few brave scholars have begun to use more
reasonable names for these functions, the old terms are still in use.
In particular, since the terms are used in the Emacs Lisp source code,
we will use them in this introduction.
Info Catalog
eintr: car cdr & cons
eintr: car & cdr