Differences

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--- ch2_3_predic [2022/02/20 06:43] – admin
+++ ch2_3_predic [2022/03/30 04:28] (current) – admin
@@ Line 1: / Line 1: @@
 **//Predicates//**
-Simple functions that return ''T'' or ''NIL''.
+Simple functions that return ''T'' or ''NIL''. They have no side effects.
 ''EQ''
@@ Line 17: / Line 17: @@
 ''EQUAL''
 Tests if two things are the same, is case and type senstive.
+<code lisp>
+>(equal "aa" "AA")
+NIL
+>(equal 1 1.0)   ; different type
+NIL
+</code>
 ''NOT''
@@ Line 64: / Line 72: @@
 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.
 <code lisp>
@@ Line 76: / Line 80: @@
 T
->(proper-list-p (cons 'a 'b)) ; this is conscell with B in cdr
+>(listp (cons 'a 'b)) ; this is conscell with B in cdr, improper list
+T
+</code>
+''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.
+<code lisp>
+>(proper-list-p (cons 'a 'b)) ; this is conscell with B in cdr, improper list
 NIL
 </code>
 ''SYMBOLP''
+Tests if the argument is a symbol. All versions of NIL are symbol.
+<code lisp>
+>(symbolp 'a)          ; symbol A
+T
+>(symbolp 13)
+NIL
+>(symbolp nil)          ; symbol NIL
+T
+</code>
 ''STRINGP''
+Tests if the argument is a string.
+<code lisp>
+>(stringp "hello")
+T
+>(stringp 'hello)
+NIL
+</code>
 ''NUMBERP''
+Tests if the argument is a number (integer or float).
+<code lisp>
+>(numberp pi)
+T
+>(numberp (/ 10 5))
+T
+>(numberp (/ 10 0))
+;Division by zero.
+NIL
+</code>
 ''INTEGERP''
+Tests if the argument is a integer number.
+<code lisp>
+>(integerp (/ 10 5))     ; integer division
+T
+>(integerp (/ 10 5.0))   ; poisoned by float 5.0
+NIL
+</code>
 ''ZEROP''
+Tests if the argument is number zero.
+<code lisp>
+>(zerop (- 10 10))
+T
+>(zerop nil)
+;Applying ZEROP on non-numeric data type!
+NIL
+</code>
 ''ODDP''
+Tests if the argument is an odd integer.
+<code lisp>
+>(oddp 3)
+T
+>(oddp 3.0)
+;Applying ODDP on non-integral number!
+NIL
+</code>
 ''EVENP''
+Tests if the argument is an even integer.
+<code lisp>
+>(evenp 2)
+T
+>(evenp 0)
+T
+</code>
 ''FUNCTIONP''
+Tests if the argument is a function object.
+<code lisp>
+>(functionp #'+)
+T
+</code>
 ''PACKAGEP''
+Tests if the argument is a package object.
+<code lisp>
+>(packagep *package*)
+T
+</code>
 ''BOUNDP''
+Expects symbol as argument. Tests if the symbol has value binding.
+<code lisp>
+>(boundp 'pi)
+T
+</code>
 ''FBOUNDP''
+Expects symbol as argument. Tests if the symbol has function or macro binding.
+<code lisp>
+>(fboundp '+)
+T
+>(fboundp 'if)    ; also works for special forms
+T
+</code>
 ''SPECIAL-OPERATOR-P''
+Expects symbol as argument. Tests if the symbol represents special operator.
+<code lisp>
+>(special-operator-p '+)     ; ordinary function
+NIL
+>(special-operator-p 'if)    ; special operator IF
+T
+</code>