zl:1 - FTP

check-type 86
I
check-type place type &optional (type-string 'nil) Macro
check-type signals an error if the contents of place are not of the desired
type. If you continue from this error, you will be asked for a new value;
check-type stores the new value in place and starts over, checking the type
of the new value and signalling another error if it is still not of the desired
type. Subforms of place cal) be evaluated multiple times because of the implicit
loop generated. check-type returns nil.
place must be a generalized variable reference acceptable to the macro setf.
type must be a type specifier; it is not evaluated. For standard Symbolics
Common Lisp type specifiers: See the section "Type Specifiers" in Symbolics
Common Lisp: Language Concepts.
type-string should be an English description of the type, starting with an indefinite
article ("a" or "an"); it is evaluated. If type-string is not supplied,
it is computed automatically from type. This optional argument is allowed
because some applications of check-type may require a more specific
description of what is wanted than can be generated automatically from the
type specifier.
The error message mentions place, its contents, and the desired type.
Examples:
(setq bees '(bumble wasp jacket» => (BUMBLE WASP JACKET)
(check-type bees (vector integer »
=> Error: The value of BEES in SI:*EVAL. (BUMBLE WASP JACKET),
was of the wrong type.
The function expected a vector whose typical element
is an integer.
(setq naards 'foo) => FDD
(check-type naards (integer e *) "a positive integer")
=> Error: The value of NAARDS in SI:*EVAL, FDD, was of the wrong
type.
The function expected a positive integer.
See the section "Data Types and Type Specifiers" in Symbolics Common
Lisp: Language Concepts.
circular-list &rest args Function
circular-list constructs a circular list whose elements are args, repeated infinitely.
circular-list is the same as list except that the list itself is used
as the last cdr, instead of nil. circular-list is especially useful with mapcar,
as in the expression: