CLHS: Glossary-Section D

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D

data type n. Trad. a type.

debug I/O n. the bidirectional stream that is the value of the variable *debug-io*.

debugger n. a facility that allows the user to handle a condition interactively. For example, the debugger might permit interactive selection of a restart from among the active restarts, and it might perform additional implementation-defined services for the purposes of debugging.

declaration n. a global declaration or local declaration.

declaration identifier n. one of the symbols declaration, dynamic-extent, ftype, function, ignore, inline, notinline, optimize, special, or type; or a symbol which is the name of a type; or a symbol which has been declared to be a declaration identifier by using a declaration declaration.

declaration specifier n. an expression that can appear at top level of a declare expression or a declaim form, or as the argument to proclaim, and which has a car which is a declaration identifier, and which has a cdr that is data interpreted according to rules specific to the declaration identifier.

declare v. to establish a declaration. See declare, declaim, or proclaim.

decline v. (of a handler) to return normally without having handled the condition being signaled, permitting the signaling process to continue as if the handler had not been present.

decoded time n. absolute time, represented as an ordered series of nine objects which, taken together, form a description of a point in calendar time, accurate to the nearest second (except that leap seconds are ignored). See Section 25.1.4.1 (Decoded Time).

default method n. a method having no parameter specializers other than the class t. Such a method is always an applicable method but might be shadowed[2] by a more specific method.

defaulted initialization argument list n. a list of alternating initialization argument names and values in which unsupplied initialization arguments are defaulted, used in the protocol for initializing and reinitializing instances of classes.

define-method-combination arguments lambda list n. a lambda list used by the `:arguments` option to define-method-combination. See Section 3.4.10 (Define-method-combination Arguments Lambda Lists).

define-modify-macro lambda list n. a lambda list used by define-modify-macro. See Section 3.4.9 (Define-modify-macro Lambda Lists).

defined name n. a symbol the meaning of which is defined by Common Lisp.

defining form n. a form that has the side-effect of establishing a definition. ``defun and defparameter are defining forms.''

defsetf lambda list n. a lambda list that is like an ordinary lambda list except that it does not permit `&aux` and that it permits use of `&environment`. See Section 3.4.7 (Defsetf Lambda Lists).

deftype lambda list n. a lambda list that is like a macro lambda list except that the default value for unsupplied optional parameters and keyword parameters is the symbol * (rather than nil). See Section 3.4.8 (Deftype Lambda Lists).

denormalized adj., ANSI, IEEE (of a float) conforming to the description of ``denormalized'' as described by IEEE Standard for Binary Floating-Point Arithmetic. For example, in an implementation where the minimum possible exponent was `-7` but where `0.001` was a valid mantissa, the number `1.0e-10` might be representable as `0.001e-7` internally even if the normalized representation would call for it to be represented instead as `1.0e-10` or `0.1e-9`. By their nature, denormalized floats generally have less precision than normalized floats.

derived type n. a type specifier which is defined in terms of an expansion into another type specifier. deftype defines derived types, and there may be other implementation-defined operators which do so as well.

derived type specifier n. a type specifier for a derived type.

designator n. an object that denotes another object. In the dictionary entry for an operator if a parameter is described as a designator for a type, the description of the operator is written in a way that assumes that appropriate coercion to that type has already occurred; that is, that the parameter is already of the denoted type. For more detailed information, see Section 1.4.1.5 (Designators).

destructive adj. (of an operator) capable of modifying some program-visible aspect of one or more objects that are either explicit arguments to the operator or that can be obtained directly or indirectly from the global environment by the operator.

destructuring lambda list n. an extended lambda list used in destructuring-bind and nested within macro lambda lists. See Section 3.4.5 (Destructuring Lambda Lists).

different adj. not the same ``The strings `"FOO"` and `"foo"` are different under equal but not under equalp.''

digit n. (in a radix) a character that is among the possible digits (`0` to `9`, `A` to `Z`, and `a` to `z`) and that is defined to have an associated numeric weight as a digit in that radix. See Section 13.1.4.6 (Digits in a Radix).

dimension n. 1. a non-negative integer indicating the number of objects an array can hold along one axis. If the array is a vector with a fill pointer, the fill pointer is ignored. ``The second dimension of that array is 7.'' 2. an axis of an array. ``This array has six dimensions.''

direct instance n. (of a class C) an object whose class is C itself, rather than some subclass of C. ``The function make-instance always returns a direct instance of the class which is (or is named by) its first argument.''

direct subclass n. (of a class C1) a class C2, such that C1 is a direct superclass of C2.

direct superclass n. (of a class C1) a class C2 which was explicitly designated as a superclass of C1 in the definition of C1.

disestablish v.t. to withdraw the establishment of an object, a binding, an exit point, a tag, a handler, a restart, or an environment.

disjoint n. (of types) having no elements in common.

dispatching macro character n. a macro character that has an associated table that specifies the function to be called for each character that is seen following the dispatching macro character. See the function make-dispatch-macro-character.

displaced array n. an array which has no storage of its own, but which is instead indirected to the storage of another array, called its target, at a specified offset, in such a way that any attempt to access the displaced array implicitly references the target array.

distinct adj. not identical.

documentation string n. (in a defining form) A literal string which because of the context in which it appears (rather than because of some intrinsically observable aspect of the string) is taken as documentation. In some cases, the documentation string is saved in such a way that it can later be obtained by supplying either an object, or by supplying a name and a ``kind'' to the function documentation. ``The body of code in a defmacro form can be preceded by a documentation string of kind function.''

dot n. the standard character that is variously called ``full stop,'' ``period,'' or ``dot'' (`.`). See Figure 2-5.

dotted list n. a list which has a terminating atom that is not nil. (An atom by itself is not a dotted list, however.)

dotted pair n. 1. a cons whose cdr is a non-list. 2. any cons, used to emphasize the use of the cons as a symmetric data pair.

double float n. an object of type double-float.

double-quote n. the standard character that is variously called ``quotation mark'' or ``double quote'' (`"`). See Figure 2-5.

dynamic binding n. a binding in a dynamic environment.

dynamic environment n. that part of an environment that contains bindings with dynamic extent. A dynamic environment contains, among other things: exit points established by unwind-protect, and bindings of dynamic variables, exit points established by catch, condition handlers, and restarts.

dynamic extent n. an extent whose duration is bounded by points of establishment and disestablishment within the execution of a particular form. See indefinite extent. ``Dynamic variable bindings have dynamic extent.''

dynamic scope n. indefinite scope along with dynamic extent.

dynamic variable n. a variable the binding for which is in the dynamic environment. See special.

The following X3J13 cleanup issues, not part of the specification, apply to this section:

- DEFTYPE-DESTRUCTURING:YES
- DEFTYPE-KEY:ALLOW
- SYNTACTIC-ENVIRONMENT-ACCESS:RETRACTED-MAR91

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