Predicate Functions

(atom <expr>)  IS THIS AN ATOM?
    <expr>      the expression to check
    returns     t if the value is an atom, nil otherwise

(symbolp <expr>)  IS THIS A SYMBOL?
    <expr>      the expression to check
    returns     t if the expression is a symbol, nil otherwise

(numberp <expr>)  IS THIS A NUMBER?
    <expr>      the expression to check
    returns     t if the expression is a number, nil otherwise

(null <expr>)  IS THIS AN EMPTY LIST?
    <expr>      the list to check
    returns     t if the list is empty, nil otherwise

(not <expr>)  IS THIS FALSE?
    <expr>      the expression to check
    return      t if the value is nil, nil otherwise

(listp <expr>)  IS THIS A LIST?
    <expr>      the expression to check
    returns     t if the value is a cons or nil, nil otherwise

(endp <list>)  IS THIS THE END OF A LIST
    <list>      the list
    returns     t if the value is nil, nil otherwise

(consp <expr>)  IS THIS A NON-EMPTY LIST?
    <expr>      the expression to check
    returns     t if the value is a cons, nil otherwise

(integerp <expr>)  IS THIS AN INTEGER?
    <expr>      the expression to check
    returns     t if the value is an integer, nil otherwise

(floatp <expr>)  IS THIS A FLOAT?
    <expr>      the expression to check
    returns     t if the value is a float, nil otherwise

(stringp <expr>)  IS THIS A STRING?
    <expr>      the expression to check
    returns     t if the value is a string, nil otherwise

(characterp <expr>)  IS THIS A CHARACTER?
    <expr>      the expression to check
    returns     t if the value is a character, nil otherwise

(arrayp <expr>)  IS THIS AN ARRAY?
    <expr>      the expression to check
    returns     t if the value is an array, nil otherwise

(streamp <expr>)  IS THIS A STREAM?
    <expr>      the expression to check
    returns     t if the value is a stream, nil otherwise

(objectp <expr>)  IS THIS AN OBJECT?
    <expr>      the expression to check
    returns     t if the value is an object, nil otherwise

#ifdef WINTERP
(widgetobjp <expr>)  IS THIS A WIDGETOBJ?
    <expr>      the expression to check
    returns     t if the value is an object, nil otherwise
#endif

(boundp <sym>)  IS A VALUE BOUND TO THIS SYMBOL?
    <sym>       the symbol
    returns     t if a value is bound to the symbol, nil otherwise

(fboundp <sym>)  IS A FUNCTIONAL VALUE BOUND TO THIS SYMBOL?
    <sym>       the symbol
    returns     t if a functional value is bound to the symbol,
                nil otherwise

(minusp <expr>)  IS THIS NUMBER NEGATIVE?
    <expr>      the number to test
    returns     t if the number is negative, nil otherwise

(zerop <expr>)  IS THIS NUMBER ZERO?
    <expr>      the number to test
    returns     t if the number is zero, nil otherwise

(plusp <expr>)  IS THIS NUMBER POSITIVE?
    <expr>      the number to test
    returns     t if the number is positive, nil otherwise

(evenp <expr>)  IS THIS INTEGER EVEN?
    <expr>      the integer to test
    returns     t if the integer is even, nil otherwise

(oddp <expr>)  IS THIS INTEGER ODD?
    <expr>      the integer to test
    returns     t if the integer is odd, nil otherwise

(eq <expr1> <expr2>)  ARE THE EXPRESSIONS IDENTICAL?
    <expr1>     the first expression
    <expr2>     the second expression
    returns     t if they are equal, nil otherwise

(eql <expr1> <expr2>)  ARE THE EXPRESSIONS IDENTICAL?
                        (WORKS WITH ALL NUMBERS)
    <expr1>     the first expression
    <expr2>     the second expression
    returns     t if they are equal, nil otherwise

(equal <expr1> <expr2>)  ARE THE EXPRESSIONS EQUAL?
    <expr1>     the first expression
    <expr2>     the second expression
    returns     t if they are equal, nil otherwise