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Predicates
Simple functions that return T or NIL.
EQ
Tests if to arguments are the same symbol, accepts only symbols or NIL.
>(eq 'pi 'user::pi) T >(eq 'nil ()) ; NIL, 'NIL, () and '() are all EQ T
EQUAL
Tests if two things are the same, is case and type senstive.
NOT
Logical not. Accepts single argument.
>(not 13) NIL >(not '()) T
ATOM
Tests if the argument is an atom.
>(atom 13) T >(atom nil) ; NIL is an atom (and list) T >(atom '()) ; this is still NIL T >(atom '(a b)) ; this is list NIL
CONSP
Tests if the argument is a cons cell.
>(consp '()) ; NIL is not cons NIL >(consp '(a b)) T
LISTP
Tests if the argument is a list, that means cons-cell or nil.
>(listp nil) ; NIL is a list (and atom) T >(listp '(a b)) T >(listp (cons 'a 'b)) ; this is conscell with B in cdr, improper list T
PROPER-LIST-P
Tests if the argument is a proper list. Proper list means list ending with NIL in the cdr of the last cons cell. Improper list might be dotted, or even cyclic.
>(proper-list-p (cons 'a 'b)) ; this is conscell with B in cdr, improper list NIL
SYMBOLP
Tests if the argument is symbol. All versions of NIL are symbol.
>(symbolp 'a) ; symbol A T >(symbolp 13) NIL >(symbolp nil) ; symbol NIL T
STRINGP
Tests if the argument is a string.
>(stringp "hello") T >(stringp 'hello) NIL
NUMBERP
INTEGERP
ZEROP
ODDP
EVENP
FUNCTIONP
PACKAGEP
BOUNDP
FBOUNDP
SPECIAL-OPERATOR-P