CLHS: Glossary-Section P

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P

package n. an object of type package.

package cell n. Trad. (of a symbol) The place in a symbol that holds one of possibly several packages in which the symbol is interned, called the home package, or which holds nil if no such package exists or is known. See the function symbol-package.

package designator n. a designator for a package; that is, an object that denotes a package and that is one of: a string designator (denoting the package that has the string that it designates as its name or as one of its nicknames), or a package (denoting itself).

package marker n. a character which is used in the textual notation for a symbol to separate the package name from the symbol name, and which is colon in the standard readtable. See Section 2.1 (Character Syntax).

package prefix n. a notation preceding the name of a symbol in text that is processed by the Lisp reader, which uses a package name followed by one or more package markers, and which indicates that the symbol is looked up in the indicated package.

package registry n. A mapping of names to package objects. It is possible for there to be a package object which is not in this mapping; such a package is called an unregistered package. Operators such as find-package consult this mapping in order to find a package from its name. Operators such as do-all-symbols, find-all-symbols, and list-all-packages operate only on packages that exist in the package registry.

pairwise adv. (of an adjective on a set) applying individually to all possible pairings of elements of the set. ``The types A, B, and C are pairwise disjoint if A and B are disjoint, B and C are disjoint, and A and C are disjoint.''

parallel adj. Trad. (of binding or assignment) done in the style of psetq, let, or do; that is, first evaluating all of the forms that produce values, and only then assigning or binding the variables (or places). Note that this does not imply traditional computational ``parallelism'' since the forms that produce values are evaluated sequentially. See sequential.

parameter n. 1. (of a function) a variable in the definition of a function which takes on the value of a corresponding argument (or of a list of corresponding arguments) to that function when it is called, or which in some cases is given a default value because there is no corresponding argument. 2. (of a format directive) an object received as data flow by a format directive due to a prefix notation within the format string at the format directive's point of use. See Section 22.3 (Formatted Output). ``In `"~3,'0D"`, the number `3` and the character `#\0` are parameters to the `~D` format directive.''

parameter specializer n. 1. (of a method) an expression which constrains the method to be applicable only to argument sequences in which the corresponding argument matches the parameter specializer. 2. a class, or a list `(eql` object`)`.

parameter specializer name n. 1. (of a method definition) an expression used in code to name a parameter specializer. See Section 7.6.2 (Introduction to Methods). 2. a class, a symbol naming a class, or a list `(eql` form`)`.

pathname n. an object of type pathname, which is a structured representation of the name of a file. A pathname has six components: a ``host,'' a ``device,'' a ``directory,'' a ``name,'' a ``type,'' and a ``version.''

pathname designator n. a designator for a pathname; that is, an object that denotes a pathname and that is one of: a pathname namestring (denoting the corresponding pathname), a stream associated with a file (denoting the pathname used to open the file; this may be, but is not required to be, the actual name of the file), or a pathname (denoting itself). See Section 21.1.1.1.2 (Open and Closed Streams).

physical pathname n. a pathname that is not a logical pathname.

place n. 1. a form which is suitable for use as a generalized reference. 2. the conceptual location referred to by such a place[1].

plist ['pee,list] n. a property list.

portable adj. (of code) required to produce equivalent results and observable side effects in all conforming implementations.

potential copy n. (of an object O1 subject to constriants) an object O2 that if the specified constraints are satisfied by O1 without any modification might or might not be identical to O1, or else that must be a fresh object that resembles a copy of O1 except that it has been modified as necessary to satisfy the constraints.

potential number n. A textual notation that might be parsed by the Lisp reader in some conforming implementation as a number but is not required to be parsed as a number. No object is a potential number---either an object is a number or it is not. See Section 2.3.1.1 (Potential Numbers as Tokens).

pprint dispatch table n. an object that can be the value of *print-pprint-dispatch* and hence can control how objects are printed when *print-pretty* is true. See Section 22.2.1.4 (Pretty Print Dispatch Tables).

predicate n. a function that returns a generalized boolean as its first value.

present n. 1. (of a feature in a Lisp image) a state of being that is in effect if and only if the symbol naming the feature is an element of the features list. 2. (of a symbol in a package) being accessible in that package directly, rather than being inherited from another package.

pretty print v.t. (an object) to invoke the pretty printer on the object.

pretty printer n. the procedure that prints the character representation of an object onto a stream when the value of *print-pretty* is true, and that uses layout techniques (e.g., indentation) that tend to highlight the structure of the object in a way that makes it easier for human readers to parse visually. See the variable *print-pprint-dispatch* and Section 22.2 (The Lisp Pretty Printer).

pretty printing stream n. a stream that does pretty printing. Such streams are created by the function pprint-logical-block as a link between the output stream and the logical block.

primary method n. a member of one of two sets of methods (the set of auxiliary methods is the other) that form an exhaustive partition of the set of methods on the method's generic function. How these sets are determined is dependent on the method combination type; see Section 7.6.2 (Introduction to Methods).

primary value n. (of values resulting from the evaluation of a form) the first value, if any, or else nil if there are no values. ``The primary value returned by truncate is an integer quotient, truncated toward zero.''

principal adj. (of a value returned by a Common Lisp function that implements a mathematically irrational or transcendental function defined in the complex domain) of possibly many (sometimes an infinite number of) correct values for the mathematical function, being the particular value which the corresponding Common Lisp function has been defined to return.

print name n. Trad. (usually of a symbol) a name[3].

printer control variable n. a variable whose specific purpose is to control some action of the Lisp printer; that is, one of the variables in Figure 22-1, or else some implementation-defined variable which is defined by the implementation to be a printer control variable.

printer escaping n. The combined state of the printer control variables *print-escape* and *print-readably*. If the value of either *print-readably* or *print-escape* is true, then printer escaping is ``enabled''; otherwise (if the values of both *print-readably* and *print-escape* are false), then printer escaping is ``disabled''.

printing adj. (of a character) being a graphic character other than space.

process v.t. (a form by the compiler) to perform minimal compilation, determining the time of evaluation for a form, and possibly evaluating that form (if required).

processor n., ANSI an implementation.

proclaim v.t. (a proclamation) to establish that proclamation.

proclamation n. a global declaration.

prog tag n. Trad. a go tag.

program n. Trad. Common Lisp code.

programmer n. an active entity, typically a human, that writes a program, and that might or might not also be a user of the program.

programmer code n. code that is supplied by the programmer; that is, code that is not system code.

proper list n. A list terminated by the empty list. (The empty list is a proper list.) See improper list.

proper name n. (of a class) a symbol that names the class whose name is that symbol. See the functions class-name and find-class.

proper sequence n. a sequence which is not an improper list; that is, a vector or a proper list.

proper subtype n. (of a type) a subtype of the type which is not the same type as the type (i.e., its elements are a ``proper subset'' of the type).

property n. (of a property list) 1. a conceptual pairing of a property indicator and its associated property value on a property list. 2. a property value.

property indicator n. (of a property list) the name part of a property, used as a key when looking up a property value on a property list.

property list n. 1. a list containing an even number of elements that are alternating names (sometimes called indicators or keys) and values (sometimes called properties). When there is more than one name and value pair with the identical name in a property list, the first such pair determines the property. 2. (of a symbol) the component of the symbol containing a property list.

property value n. (of a property indicator on a property list) the object associated with the property indicator on the property list.

purports to conform v. makes a good-faith claim of conformance. This term expresses intention to conform, regardless of whether the goal of that intention is realized in practice. For example, language implementations have been known to have bugs, and while an implementation of this specification with bugs might not be a conforming implementation, it can still purport to conform. This is an important distinction in certain specific cases; e.g., see the variable *features*.

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

- PLIST-DUPLICATES:ALLOW
- PRINT-READABLY-BEHAVIOR:CLARIFY
- PATHNAME-HOST-PARSING:RECOGNIZE-LOGICAL-HOST-NAMES
- PATHNAME-LOGICAL:ADD
- CLASS-OBJECT-SPECIALIZER:AFFIRM

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