PREDICATE FUNCTIONS

IS THIS AN ATOM?

(atom <expr>)

<expr> the expression to check

returns t if the value is an atom, NIL otherwise

IS THIS A SYMBOL?

(symbolp <expr>)

<expr> the expression to check

returns t if the expression is a symbol, NIL otherwise

IS THIS A NUMBER?

(numberp <expr>)

<expr> the expression to check

returns t if the expression is a number, NIL otherwise

IS THIS AN EMPTY LIST?

(null <expr>)

<expr> the list to check

returns t if the list is empty, NIL otherwise

IS THIS FALSE?

(not <expr>)

<expr> the expression to check

return t if the value is NIL, NIL otherwise

IS THIS A LIST?

(listp <expr>)

<expr> the expression to check

returns t if the value is a cons or NIL, NIL otherwise

IS THIS THE END OF A LIST?

(endp <list>)

<list> the list

returns t if the value is NIL, NIL otherwise

IS THIS A NON-EMPTY LIST?

(consp <expr>)

<expr> the expression to check

returns t if the value is a cons, NIL otherwise

IS THIS A CONSTANT?

(constantp <expr>)

<expr> the expression to check

returns t if the value is a constant (basically, would EVAL <expr> repeatedly return the same thing?), NIL otherwise.

IS THIS A SPECIAL SYMBOL?

(specialp <expr>)

<expr> the expression to check

returns t if the value is a symbol which is SPECIAL, NIL otherwise.

IS THIS AN INTEGER?

(integerp <expr>)

<expr> the expression to check

returns t if the value is an integer, NIL otherwise

IS THIS A FLOAT?

(floatp <expr>)

<expr> the expression to check

returns t if the value is a float, NIL otherwise

IS THIS A RATIONAL NUMBER?

(rationalp <expr>)

Part of math extension.

<expr> the expression to check

returns t if the value is rational (integer or ratio), NIL otherwise

IS THIS A COMPLEX NUMBER?

(complexp <expr>)

Part of math extension.

<expr> the expression to check

returns t if the value is a complex number, NIL otherwise

IS THIS A STRING?

(stringp <expr>)

<expr> the expression to check

returns t if the value is a string, NIL otherwise

IS THIS A CHARACTER?

(characterp <expr>)

<expr> the expression to check

returns t if the value is a character, NIL otherwise

IS THIS AN ARRAY?

(arrayp <expr>)

<expr> the expression to check

returns t if the value is an array, NIL otherwise

IS THIS A STREAM?

(streamp <expr>)

<expr> the expression to check

returns t if the value is a stream, NIL otherwise

IS STREAM OPEN?

(open-stream-p <stream>)

<stream> the stream

returns t if the stream is open, NIL otherwise

IS STREAM READABLE?

(input-stream-p <stream>)

<stream> the stream

returns t if stream is readable, NIL otherwise

IS STREAM WRITABLE?

(output-stream-p <stream>)

<stream> the stream

returns t if stream is writable, NIL otherwise

IS THIS AN OBJECT?

(objectp <expr>)

<expr> the expression to check

returns t if the value is an object, NIL otherwise

IS THIS A CLASS OBJECT?

(classp <expr>)

<expr> the expression to check

returns t if the value is a class object, NIL otherwise

IS A VALUE BOUND TO THIS SYMBOL?

(boundp <sym>)

<sym> the symbol

returns t if a value is bound to the symbol, NIL otherwise

IS A FUNCTIONAL VALUE BOUND TO THIS SYMBOL?

(fboundp <sym>)

<sym> the symbol

returns t if a functional value is bound to the symbol, NIL otherwise

IS THIS A FUNCTION?

(functionp <sym>)

Defined in common.lsp

<expr> the expression to check

returns t if the value is a function -- that is, can it be applied to arguments. This is true for any symbol (even those with no function binding), list with car being lambda, a closure, or subr. Otherwise returns NIL.

IS THIS NUMBER NEGATIVE?

(minusp <expr>)

<expr> the number to test

returns t if the number is negative, NIL otherwise

IS THIS NUMBER ZERO?

(zerop <expr>)

<expr> the number to test

returns t if the number is zero, NIL otherwise

IS THIS NUMBER POSITIVE?

(plusp <expr>)

<expr> the number to test

returns t if the number is positive, NIL otherwise

IS THIS INTEGER EVEN?

(evenp <expr>)

<expr> the integer to test

returns t if the integer is even, NIL otherwise

IS THIS INTEGER ODD?

(oddp <expr>)

<expr> the integer to test

returns t if the integer is odd, NIL otherwise

IS SET A SUBSET?

(subsetp <list1> <list2> &key :test :test-not :key)

<list1> the first list

<list2> the second list

:test test function (defaults to eql)
:test-not test function (sense inverted)
:key function to apply to test function arguments (defaults to identity)
returns t if every element of the first list is in the second list, NIL otherwise

ARE THE EXPRESSIONS EQUAL?

(eq <expr1> <expr2>)

(eql <expr1> <expr2>)

(equal <expr1> <expr2>)

(equalp <expr1> <expr2>)

equalp defined in common.lsp

<expr1> the first expression

<expr2> the second expression

returns t if equal, NIL otherwise. Each is progressively more liberal in what is "equal":

eq: identical pointers works with characters, symbols, and arbitrarily small integers
eql: works with all numbers, if same type (see also = on page 57)
equal: lists and strings
equalp: case insensitive characters (and strings), numbers of differing types, arrays (which can be equalp to string containing same elements)

IS THIS A SPECIFIED TYPE?

(typep <expr> <type>)

<expr> the expression to test

<type> the type specifier. Symbols can either be one of those listed under type-of (on page 88) or one of:

The specifer can also be a form (which can be nested). All form elements are quoted. Valid form cars:

or any of the cdr type specifiers must be true
and all of the cdr type specifiers must be true
not the single cdr type specifier must be false
satisfies the result of applying the cdr predicate function to <expr>
member <expr> must be eql to one of the cdr values
object <expr> must be an object, of class specified by the single cdr value. The cdr value can be a symbol which must evaluate to a class.

Note that everything is of type T, and nothing is of type NIL.

returns t if <expr> is of type <type>, NIL otherwise.

XLISP-PLUS - Version 2.1g - Tom Almy tom.almy@tek.com - 18 JUL 94

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