Burke_et_al-NIL_Reference_Manual_0286-1984

Cotl\'cnliot1s 2 Nil. Manual
'n1e names of predicate functions in!\u, and CO:\fMON LISP are typically fi)nned by suffixing
the character t~p" to the end of a descriptive name. For instance.consp is a predicate which is
true if its argument is a cons~ and lessp (which actuaUy is a MACUSP. not COMMON USP.
function) compares numbers and (when given two arguments) returns t if the first is less than the
second. If the name itself is hyphenated. then "-pit is suffixed: upper-case-p is a predicate
which tells if a character is upper-case. If, however. the predicate name is fonncd by prefixing a
specializing name to an existing predicate name, then the final t.p" would not have hyphenation
added to it: string-Iessp is a predicate can be used to compare strings using a standard collating
sequence. the name heing fimned by prefixing "string-" to 'tlessp". There are. of coursc. many
exceptions to this. and this convention does nOl eliminate all ambiguity. but it helps. A goud
numher of ~II functions did not fi)Uow this convention in earlier versiul1sof. ~II: many of these
h~l\'e heen fixed. mld the old names made synonymous with the new names for the time being.
MC:NJLMAN;INTRO 18
23-DFC-83