LabLISP Guide

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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.

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.

>(listp nil)          ; NIL is a list (and atom)
T
 
>(listp '(a b))
T
 
>(proper-list-p (cons 'a 'b)) ; this is conscell with B in cdr
NIL

SYMBOLP

STRINGP

NUMBERP

INTEGERP

ZEROP

ODDP

EVENP

FUNCTIONP

PACKAGEP

BOUNDP

FBOUNDP

SPECIAL-OPERATOR-P