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- PSL Manual 7 February 1983 Identifiers
- section 6.0 page 6.1
- CHAPTER 6
CHAPTER 6
CHAPTER 6
- IDENTIFIERS
IDENTIFIERS
IDENTIFIERS
- 6.1. Introduction . . . . . . . . . . . . . . . 6.1
- 6.2. Fields of Ids . . . . . . . . . . . . . . . 6.2
- 6.3. Identifiers and the Id-Hash-Table . . . . . . . . 6.2
- 6.3.1. Identifier Functions . . . . . . . . . . 6.3
- 6.3.2. Find. . . . . . . . . . . . . . . . 6.4
- 6.4. Property List Functions. . . . . . . . . . . . 6.5
- 6.4.1. Functions for Flagging Ids . . . . . . . . 6.6
- 6.4.2. Direct Access to the Property Cell. . . . . . 6.7
- 6.5. Value Cell Functions. . . . . . . . . . . . . 6.7
- 6.6. Package System Functions . . . . . . . . . . . 6.10
- 6.7. System Global Variables, Switches and Other "Hooks" . . 6.13
- 6.7.1. Introduction . . . . . . . . . . . . . 6.13
- 6.7.2. Setting Switches. . . . . . . . . . . . 6.14
- 6.7.3. Special Global Variables . . . . . . . . . 6.15
- 6.7.4. Special Put Indicators. . . . . . . . . . 6.15
- 6.7.5. Special Flag Indicators . . . . . . . . . 6.16
- 6.7.6. Displaying Information About Globals . . . . . 6.16
- 6.1. Introduction
6.1. Introduction
6.1. Introduction
- __________ __ __________
In PSL variables are called identifiers or ids. An identifier is
- implemented as a tagged data object (described in Chapter 4) containing a
- __ _____
pointer or offset into a five item structure - the id space. One item in
- this structure is called the print name, which is the external
- __
representation of the id.
- __ ____ _____
The interpreter uses an id hash table to get from the print name of an
- __________ __ _____ __ _____ __ ____
identifier to its entry in the id space. The id space and the id hash
- _____
table are described below.
- Sometimes there is a need for more than one name space when one is
- building a large system. For example, one may wish to allow several
- programmers to each produce a part of a system without having to worry
- about name conflicts. PSL provides a package system for this purpose,
- __ ____ _____
giving the user a tree-structured id hash table.
Identifiers 7 February 1983 PSL Manual
- page 6.2 section 6.2
- 6.2. Fields of Ids
6.2. Fields of Ids
6.2. Fields of Ids
- __ ____ ____ ____
An id is an item with an info field; the info field is an offset into a
- __ _____ ____
special id space consisting of structures of 5 fields. The fields (items)
- are:
- _____ ____ ______
print-name The print name points at a string of characters which is the
- __________
external representation of the identifier. The syntax for
- __________
identifiers is described in Section 12.5 on reading
- functions.
- ________ ____
property-cell One may want to associate various flags and properties with
- __________
an identifier. These can be stored on a property-list for
- __
an id, flags by name and properties by an (indicator .
- __
value) pair. The property cell of an id contains a pointer
- to this list. Access is by means of functions defined in
- Section 6.4.
- _____ ____ __________
value-cell The value of the identifier or a pointer to the value in the
- heap is stored in this field. If no value exists, this cell
- __________
contains an unbound identifier indicator. These cells can
- be accessed by functions defined in this chapter.
- _____
_____
_____
macro
________ ____ ________ macro
function-cell An id may have a function or macro associated with it.
- PutD GetD RemD
PutD GetD RemD
Access is by means of the PutD, GetD, and RemD functions
- defined in Section 10.1.2.
- _______ ____
package-cell PSL permits the use of a multiple package facility (multiple
- __ ____ _____
id hash table). The package cell refers to the appropriate
- __ ____ _____
id hash table.
- 6.3. Identifiers and the Id hash table
6.3. Identifiers and the Id hash table
6.3. Identifiers and the Id hash table
- __________
The method used by PSL to retrieve information about an identifier makes
- __ ____ _____
use of the id hash table (corresponding to the Oblist, or Object list, in
- __________
some versions of LISP). A hash function is applied to the identifier name
- __ ____ _____
giving a position in the id hash table. The contents of the hash table at
- __ _____ __________
that point contain an offset into the id space. For a new identifier, the
- __ _____
next free position in the id space is found and a pointer to it is placed
- in the hash table entry.
- __
The process of putting an id into the hash table is called interning.
- __
This is done automatically by the LISP reader, so any id typed in at the
- terminal is interned. Interning can also be done by the programmer using
- Intern
Intern ______ __ __
the function Intern to convert a string to an id. An id may have an entry
- __ _____
in the id space without being interned. In fact it is possible to have
- __
several ids with the same print name, one interned and the others not.
- __
(The use of the package system allows one to have several interned ids with
- the same print name.)
- __ _____
Note that when one starts PSL, the id space already contains
- __
approximately 2000 ids. These include all of the ASCII characters, the
- functions and globals described in this manual, plus system functions and
PSL Manual 7 February 1983 Identifiers
- section 6.3 page 6.3
- globals. If a user uses any of these names for his own functions or
- globals, there can be a conflict. This is another reason for having a
- package system. A warning message appears if a user tries to redefine a
- system function.
- ? Do you really want to redefine the system function 'name? (Y or N)
- If the user answers "Y", his definition replaces the current definition.
- ________
(See Chapter 10 for a description of the switch !*USERMODE which controls
- the printing of this message.)
- __ ____ _____
Basic PSL currently provides a single id hash table. PSL provides all
- the "hooks" to permit a package system to be loaded as an option; certain
- functions are redefined in this process. If the package system is loaded,
- __ ____ _____
a tree-structured id hash table can be created in which each level can be
- __ ____ _____ __ ______
thought of as a smaller id hash table. If a new id or string is to be
- interned, it is searched for in the tree according to a specified rule.
- For more information see Section 6.6.
- __
Information on converting ids to other types can be found in Chapter
- 12 and Section 4.3.
- 6.3.1. Identifier Functions
6.3.1. Identifier Functions
6.3.1. Identifier Functions
- __________ __ ____ _____
The following functions deal with identifiers and the id hash table.
- GenSym
GenSym __ ____
(GenSym ): id expr
- __________
Creates an identifier which is not interned on the id hash table
- Eq
Eq __
and consequently not Eq to anything else. The id is derived from
- a string of the form "G0000", which is incremented upon each call
- GenSym
GenSym
to GenSym.
- [??? Is this interned or recorded on the NIL package ???]
[??? Is this interned or recorded on the NIL package ???]
[??? Is this interned or recorded on the NIL package ???]
- [??? Can we change the GenSym string ???]
[??? Can we change the GenSym string ???]
[??? Can we change the GenSym string ???]
- InternGenSym
InternGenSym __ ____
(InternGenSym ): id expr
- GenSym
GenSym __
Similar to GenSym but returns an interned id.
- StringGenSym
StringGenSym ______ ____
(StringGenSym ): string expr
- GenSym
GenSym ______
Similar to GenSym but returns a string of the form "L0000"
- __
instead of an id.
Identifiers 7 February 1983 PSL Manual
- page 6.4 section 6.3
- RemOb
RemOb _ __ _ __ ____
(RemOb U:id): U:id expr
- _
If U is present on the current package search path it is removed.
- _
This does not affect U having properties, flags, functions and
- _
the like. U is returned.
- InternP
InternP _ __ ______ _______ ____
(InternP U:{id,string}): boolean expr
- _
Returns T if U is interned in the current search path.
- MapObl
MapObl _____ ________ _________ ____
(MapObl FNAME:function): Undefined expr
- MapObl
MapObl _____ __
MapObl applies function FNAME to each id interned in the current
- hash table.
- 6.3.2. Find
6.3.2. Find
6.3.2. Find
- ______ __ __ ____
These functions take a string or id as an argument, and scan the id hash
- _____ __
table to collect a list of ids with prefix or suffix matching the argument.
- This is a loadable option (LOAD FIND).
- FindPrefix
FindPrefix ___ __ ______ __ ____ ____
(FindPrefix KEY:{id, string}): id-list expr
- __ ____ _____ __ ___
Scans current id hash table for all ids whose prefix matches KEY.
- Returns all the identifiers found as an alphabetically sorted
- list.
- FindSuffix
FindSuffix ___ __ ______ __ ____ ____
(FindSuffix KEY:{id, string}): id-list expr
- __ ____ _____ __ ___
Scans current id hash table for all ids whose suffix matches KEY.
- Returns all the identifiers found as an alphabetically sorted
- list.
- (Setq X (FindPrefix '!*) % Finds all identifiers starting with *
- (Setq Y (FindSuffix "STRING")) % Finds all identifiers ending with S
- 6.4. Property List Functions
6.4. Property List Functions
6.4. Property List Functions
- __________ ____ ____
The property cell of an identifier points to a "property list". The list
- __
is used to quickly associate an id name with a set of entities; those
- __
entities are called "flags" if their use gives the id a boolean value, and
- __
"properties" if the id is to have an arbitrary attribute (an indicator with
- a property).
PSL Manual 7 February 1983 Identifiers
- section 6.4 page 6.5
- Put
Put _ __ ___ __ ____ ___ ___ ____
(Put U:id IND:id PROP:any): any expr
- ___ ____
The indicator IND with the property PROP is placed on the
- Put
____ __ _ Put
property list of the id U. If the action of Put occurs, the
- ____ _ ___ __
value of PROP is returned. If either of U and IND are not ids
- the type mismatch error occurs and no property is placed.
- (Put 'Jim 'Height 68)
- The above returns 68 and places (Height . 68) on the property
- __
list of the id Jim.
- Get
Get _ __ ___ __ ___ ____
(Get U:id IND:id): any expr
- ___
Returns the property associated with indicator IND from the
- ____ _ _ ___
property list of U. If U does not have indicator IND, NIL is
- Get Get
Get Get
returned. (In older LISPs, Get could access functions.) Get
- _ __
returns NIL if U is not an id.
- (Get 'Jim 'Height) returns 68
- DefList
DefList _ ____ ___ __ ____ ____
(DefList U:list IND:id): list expr
- _
U is a list in which each element is a two-element list:
- __ __ ____ ___ __ _ ___
(ID:ID PROP:ANY). Each id in U has the indicator IND with
- Put
Put
property PROP placed on its property list by the Put function.
- DefList
DefList ____
The value of DefList is a list of the first elements of each
- Put DefList
Put DefList
two-element list. Like Put, DefList may not be used to define
- functions.
- (DE DEFLIST (U IND)
- (COND ((NULL U) NIL)
- (T (CONS(PROGN(PUT (CAAR U) IND (CADAR U))
- (CAAR U))
- (DEFLIST (CDR U) IND)))))
- RemProp
RemProp _ __ ___ __ ___ ____
(RemProp U:id IND:id): any expr
- ___ ____
Removes the property with indicator IND from the property list of
- _
U. Returns the removed property or NIL if there was no such
- indicator.
- RemPropL
RemPropL _ __ ____ ___ __ ___ ____
(RemPropL U:id-list IND:id): NIL expr
- ___ __ _
Remove property IND from all ids in U.
Identifiers 7 February 1983 PSL Manual
- page 6.6 section 6.4
- 6.4.1. Functions for Flagging Ids
6.4.1. Functions for Flagging Ids
6.4.1. Functions for Flagging Ids
- __
In some LISPs, flags and indicators may clash. In PSL, flags are ids and
- ____
properties are pairs on the prop-list, so no clash occurs.
- Flag
Flag _ __ ____ _ __ ___ ____
(Flag U:id-list V:id): NIL expr
- Flag Flag
Flag __ _ _ Flag
Flag flags each id in U with V; that is, the effect of Flag is
- FlagP
__ _ _ FlagP _
that for each id X in U, FlagP(X, V) has the value T. Both V and
- _ __________
all the elements of U must be identifiers or the type mismatch
- Flag
Flag __ _
error occurs. After Flagging, the id V appears on the property
- __ _
list of each id X in U. However, flags cannot be accessed,
- placed on, or removed from property lists using normal property
- Get Put RemProp
Get Put RemProp
list functions Get, Put, and RemProp. Note that if an error
- Flag
Flag __ _
occurs during execution of Flag, then some of the ids on U may be
- _
flagged with V, and others may not be. The statement below
- causes the flag "Lose" to be placed on the property lists of the
- __
ids X and Y.
- (Flag '(X Y) 'Lose)
- FlagP
FlagP _ __ _ __ _______ ____
(FlagP U:id V:id): boolean expr
- _ _
Returns T if U has been flagged with V; otherwise returns NIL.
- _ _ __
Returns NIL if either U or V is not an id.
- RemFlag
RemFlag _ __ ____ _ __ ___ ____
(RemFlag U:id-list V:id): NIL expr
- _ ____
Removes the flag V from the property list of each member of the
- ____ _ _ _ __
list U. Both V and all the elements of U must be ids or the type
- mismatch error occurs.
- Flag1
Flag1 _ __ _ ___ _________ ____
(Flag1 U:id V:any): Undefined expr
- _ __ _
Puts flag V on the property list of id U.
- RemFlag1
RemFlag1 _ __ _ ___ _________ ____
(RemFlag1 U:id V:any): Undefined expr
- _ __ _
Removes the flag V from the property list of id U.
- [??? Make Flag1 and RemFlag1 return single value. ???]
[??? Make Flag1 and RemFlag1 return single value. ???]
[??? Make Flag1 and RemFlag1 return single value. ???]
PSL Manual 7 February 1983 Identifiers
- section 6.4 page 6.7
- 6.4.2. Direct Access to the Property Cell
6.4.2. Direct Access to the Property Cell
6.4.2. Direct Access to the Property Cell
- Use of the following functions can destroy the integrity of the property
- ____
list. Since PSL uses properties at a low level, care should be taken in
- the use of these functions.
- Prop
Prop _ __ ___ ____
(Prop U:id): any expr
- ____ _
Returns the property list of U.
- SetProp
SetProp _ __ _ ___ _ ___ ____
(SetProp U:id L:any): L:any expr
- _ ____ _
Store item L as the property list of U.
- 6.5. Value Cell Functions
6.5. Value Cell Functions
6.5. Value Cell Functions
- Eval
Eval
The contents of the value cell are usually accessed by Eval (Chapter 11)
- ValueCell Set SetQ
ValueCell Set SetQ
or ValueCell (below) and changed by Set or SetQ.
- Set
Set ___ __ _____ ___ ___ ____
(Set EXP:id VALUE:any): any expr
- ___ __________
EXP must be an identifier or a type mismatch error occurs. The
- Set
Set
effect of Set is replacement of the item bound to the identifier
- _____
by VALUE. If the identifier is not a LOCAL variable or has not
- been declared GLOBAL, it is automatically declared FLUID with the
- resulting warning message:
- *** EXP declared FLUID
- ___
EXP must not evaluate to T or NIL or an error occurs:
- ***** Cannot change T or NIL
- SetQ
SetQ ________ __ _____ ___ ___ _____
(SetQ VARIABLE:id VALUE:any): any fexpr
- ________
The value of the current binding of VARIABLE is replaced by the
- _____
value of VALUE.
- (SETQ X 1)
- is equivalent to
- (SET 'X 1)
- SetQ
SetQ
SetQ now conforms to the Common LISP standard, allowing
- sequential assignment:
Identifiers 7 February 1983 PSL Manual
- page 6.8 section 6.5
- (SETQ A 1 B 2)
- ==> (SETQ A 1)
- (SETQ B 2)
- DeSetQ
DeSetQ _ ___ _ ___ _ ___ _____
(DeSetQ U:any V:any): V:any macro
- DeSetQ
DeSetQ
This is a function in "USEFUL" (Load USEFUL; in RLISP). DeSetQ
- SetQ
SetQ
is a destructuring SetQ. That is, the first argument is a piece
- SetQ
____ ____ __ SetQ
of list structure whose atoms are all ids. Each is SetQ'd to the
- corresponding part of the second argument. For instance
- (DeSetQ (a (b) . c) '((1) (2) (3) 4))
- SetQ
SetQ
SetQ's a to (1), b to 2, and c to ((3) 4).
- PSetQ
PSetQ ________ __ _____ ___ _________ _____
(PSetQ [VARIABLE:id VALUE:any]): Undefined macro
- Part of the USEFUL package (LOAD USEFUL).
- (PSETQ VAR1 VAL1 VAR2 VAL2 ... VARn VALn)
- SetQ
SetQ
SetQ's the VAR's to the corresponding VAL's. The VAL's are all
- evaluated before any assignments are made. That is, this is a
- SetQ
SetQ
parallel SetQ.
- SetF
SetF ___ ____ ___ ___ ___ ___ _____
(SetF [LHS:form RHS:any]): RHS:any macro
- SetF SetF
SetF SetF
There are two versions of SetF. SetF is redefined on loading
- SetF SetF
SetF SetF
USEFUL. The description below is for the resident SetF. SetF
- provides a method for assigning values to expressions more
- __
general than simple ids. For example:
- (SETF (CAR X) 2)
- ==> CAR X := 2;
- is equivalent to
- (RPLACA X 2)
- SetF
SetF
In general, SetF has the form
- (SetF LHS RHS)
- ___ ___
in which LHS is the "left hand side" to be assigned to and RHS is
- ___
evaluated to the value to be assigned. LHS can be one of the
- following:
- SetQ
__ SetQ
id SetQ is used to assign a value to the
PSL Manual 7 February 1983 Identifiers
- section 6.5 page 6.9
- __
id.
- Eval Set SetQ
Eval Set SetQ
(Eval expression) Set is used instead of SetQ. In
- Eval
Eval
effect, the "Eval" cancels out the
- Quote
Quote
"Quote" which would normally be used.
- Value Eval
Value Eval
(Value expression) Is treated the same as Eval.
- Car RplacA
Car ____ RplacA
(Car pair) RplacA is used to store into the Car
- "field".
- Cdr RplacD
Cdr ____ RplacD
(Cdr pair) RplacD is used to store into the Cdr
- "field".
- GetV PutV
GetV ______ PutV
(GetV vector) PutV is used to store into the
- appropriate location.
- Indx SetIndx
Indx SetIndx
(Indx "indexable object") SetIndx is used to store into the
- object.
- Sub SetSub
Sub ______ SetSub
(Sub vector) SetSub is used to store into the
- appropriate subrange of the vector.
- Car Cdr SetF
___ Car ____ Cdr ____ SetF
Note that if the LHS is (Car pair) or (Cdr pair), SetF returns
- SetF RplacA
___ SetF RplacA
the modified pair instead of the RHS, because SetF uses RplacA
- RplacD
RplacD
and RplacD in these cases.
- SetF Caar Cadr
SetF Caar Cadr
Loading USEFUL brings in declarations to SetF about Caar, Cadr,
- Cddddr
Cddddr
... Cddddr. This is rather handy with constructor/selector
- Cadadr
Cadadr
macros. For instance, if FOO is a selector which maps to Cadadr,
-
- (SETF (FOO X) Y)
- works; that is, it maps to something which does a
- (RPLACA (CDADR X) Y)
- and then returns X.
- PSetF
PSetF ___ ____ ___ ___ _________ _____
(PSetF [LHS:form RHS:any]): Undefined macro
- PSetF SetF
PSetF SetF
Part of the USEFUL package (LOAD USEFUL). PSetF does a SetF in
- ___
parallel: i.e. it evaluates all the right hand sides (RHS) before
- ___
assigning any to the left hand sides (LHS).
- MakeUnBound
MakeUnBound _ __ _________ ____
(MakeUnBound U:id): Undefined expr
- _ __
Make U an unbound id by storing a "magic" number in the value
- cell.
- ValueCell
ValueCell _ __ ___ ____
(ValueCell U:id): any expr
- __ _
Safe access to the value cell of an id. If U is not an id a type
- _
mismatch error is signalled; if U is an unbound id, an unbound id
Identifiers 7 February 1983 PSL Manual
- page 6.10 section 6.5
- _
error is signalled. Otherwise the current value of U is
- Value LispVar
Value LispVar
returned. [See also the Value and LispVar functions, described
- in Chapter 20, for more direct access].
- UnBoundP
UnBoundP _ __ _______ ____
(UnBoundP U:id): boolean expr
- _
Tests whether U has no value.
- [??? Define and describe General Property LISTs or hash-tables. See
[??? Define and describe General Property LISTs or hash-tables. See
[??? Define and describe General Property LISTs or hash-tables. See
- Hcons. ???]
Hcons. ???]
Hcons. ???]
- 6.6. Package System Functions
6.6. Package System Functions
6.6. Package System Functions
- To get the package system (Load Package). An example of the use of this
- system is at the end of this section.
- The character "\" is normally reserved in the basic Read-Table (see
- Chapter 12) to make up multi-part names of the form "PackageName\LocalId".
- If the package system is loaded, the Intern process starts searching a path
- in a linked structure from "PackageName", itself an id accessible in the
- "CurrentPackage". The print-name is still "LocalId", but the additional
- Prin1 Prin2
Prin1 Prin2
package field in each id records "PackageName". Prin1 and Prin2 are
- modified to access this field in loading the package system. The root of
- the tree is the GLOBAL package, indicated by \. If the package system is
- loaded, the basic id hash table is made into the GLOBAL package. Thus \ID
- is guaranteed in the root (in fact the pre-existing id hash table).
- [??? Explain further or at least more clearly. ???]
[??? Explain further or at least more clearly. ???]
[??? Explain further or at least more clearly. ???]
- The following fluid variables are managed by the package system.
- __________ ______
\CURRENTPACKAGE!* [Initially: Global] global
- This is the start of the search path if interning.
- \CurrentPackage!*
\CurrentPackage!*
\CurrentPackage!* is rebound in the token scanner on encountering
- a "\".
- __________ ______
\PACKAGENAMES!* [Initially: (Global)] global
- List of ALL package names currently created.
- Our current package model uses a set of general path functions that
- access functions specific to each level of the id hash table tree to do
- various things: "Localxxxx(s)" and "Pathxxxx(s)" in which "xxxx" is one of
- InternP, Intern, RemOb, MapObl
InternP, Intern, RemOb, MapObl
the set (InternP, Intern, RemOb, MapObl). By storing different functions,
- each package may have a different structure and associated functions. The
- ______
current implementation of a package uses a vector
PSL Manual 7 February 1983 Identifiers
- section 6.6 page 6.11
- [Name Father GetFn PutFn RemFn MapFn]
- __
stored under the indicator 'Package on the PackageName id.
- A simple bucket id hash table can also be used for experiments, or the
- user can build his own. As far as possible, each function checks that a
- legal package is given before performing the operation.
- [??? Should we have a package Tag ???]
[??? Should we have a package Tag ???]
[??? Should we have a package Tag ???]
- The following functions should be used.
- \CreatePackage
\CreatePackage ____ __ _____________ __ __ ____
(\CreatePackage NAME:id FATHERPACKAGE:id): id expr
- This creates a convenient size id hash table, generates the
- functions to manage it for this package, and links the new
- _____________
package to the FATHERPACKAGE so that path searches for ids are
- required.
- \SetPackage
\SetPackage ____ __ __ ____
(\SetPackage NAME:id): id expr
- ______
Selects another package such as GLOBAL\.
- \PathInternP
\PathInternP _ __ ______ _______ ____
(\PathInternP S:{id string}): boolean expr
- _
Searches from CurrentPackage!* to see if S is interned.
- \PathIntern
\PathIntern _ __ ______ __ ____
(\PathIntern S:{id string}): id expr
- __
Look up or insert an id.
- \PathRemob
\PathRemob _ __ ______ __ ____
(\PathRemob S:{id string}): id expr
- Remobs, puts in NIL package.
- \PathMapObl
\PathMapObl _ ________ ___ ____
(\PathMapObl F:function): NIL expr
- _ __
Applies F to ALL ids in path.
- \LocalInternP
\LocalInternP _ __ ______ _______ ____
(\LocalInternP S:{id string}): boolean expr
- Searches in CURRENTPACKAGE!*.
Identifiers 7 February 1983 PSL Manual
- page 6.12 section 6.6
- \LocalIntern
\LocalIntern _ __ ______ __ ____
(\LocalIntern S:{id string}): id expr
- __
Look up or insert in CURRENTPACKAGE!* (forces ids uninterned in
- CURRENTPACKAGE!* into CURRENTPACKAGE!*) .
- \LocalRemob
\LocalRemob _ __ ______ __ ____
(\LocalRemob S:{id string}): id expr
- Remobs, puts in NIL package.
- \LocalMapObl
\LocalMapObl _ ________ ___ ____
(\LocalMapObl F:function): NIL expr
- _ __
Applies F to ALL ids in (CurrentPackage!*).
- ______
Note that if a string is used, it CANNOT include the \. Also, since most
- __
ids are "RAISED" on input, be careful.
- \PathIntern
\PathIntern
Current intern, etc. are \PathIntern, etc.
- Several restrictions are placed on the use of packages when compiled.
- Since it is a loaded module and not integrated with the basic PSL system,
- all ids in the compiled package are Interned in Global\ before they are
- defined. This requires a slightly more complex loading system for
- packages. Names and function ids which conflict with names in Global\ (or
- other packages in the path) must be forced into the id hash table of the
- desired package. The package is compiled WITHOUT the package module
- loaded.
- In addition, if a function call must be issued for a function which has
- been redefined in the package the function name must be changed. When
- Fasl
Fasl
PACKAGE has been integrated with Fasl and PSL, it will be sufficient to
- prefix the function name with the package name (e.g. Global\Print).
- Currently, one must actually change the function name (e.g. Global!.Print).
- Other problems in the package system include:
- a. Single character identifiers are handled specially (i.e. not
- interned) and therefore may not be used in any packages without
- doing an explicit intern
- b. By leaving the the package identifier and '\' off the identifier
- will place it in the Global\ package instead of the current
- package
- c. If an identifier is installed in the Global\ package, then
- reference to it with another package identifier will return the
- Global\ value instead of issuing an error
- Print
Print
As an example, a small package which redefines the system function Print
PSL Manual 7 February 1983 Identifiers
- section 6.6 page 6.13
- is shown. The assumed file name is PrintPack.SL.
- (De GetFieldFn (Relation Field)
- (Slotdescslotfn
- (Cdr (Assoc Field
- (Dsdescslotalist Getdefstruct Relation)))))
- (Df Print (Args)
- (Prog (Fields)
- (Setq Fields (Get (Car Args) 'Fields))
- (Foreach Elem In (Eval (Car Args)) Do
- (Cons
- Global!.Print
- (Foreach Field In Fields Collect
- (Apply (GetFieldFn
- (Car Args) Field) ('List Elem)))))
- (Return (Car Args))))
- This package would be compiled as follows (immediately after entering
- PSL):
- (Faslout "PrintPackage")
- (Dskin "PrintPack.SL"$)
- (Faslend)
- (Quit)
- This package would be loaded as follows (immediately after entering PSL):
- (Load '(Defstruct Package))
- (CopyD 'Global!.Print Print)
- (Progn (\CreatePackage 'PrintPack 'Global)
- (\SetPAckage 'PrintPack)
- (LocalIntern 'Print))
- (Faslin "PrintPack.B")
- 6.7. System Global Variables, Switches and Other "Hooks"
6.7. System Global Variables, Switches and Other "Hooks"
6.7. System Global Variables, Switches and Other "Hooks"
- 6.7.1. Introduction
6.7.1. Introduction
6.7.1. Introduction
- A number of global variables provide global control of the LISP system,
- or implement values which are constant throughout execution. Certain
- options are controlled by switches, with T or NIL properties (e.g. ECHOing
- as a file is read in); others require a value, such as an integer for the
- current output base. PSL has the convention (following the REDUCE/RLISP
- convention) of using a "!*" in the name of the variable: !*XXXXX for GLOBAL
- variables expecting a T/NIL value (called "switches"), and XXXXX!* for
- other GLOBALs. Chapter 26 is an index of switches and global variables
- used in PSL.
Identifiers 7 February 1983 PSL Manual
- page 6.14 section 6.7
- [??? These should all be FLUIDs, so that ANY one of these variables may
[??? These should all be FLUIDs, so that ANY one of these variables may
[??? These should all be FLUIDs, so that ANY one of these variables may
- be rebound, as appropriate ???]
be rebound, as appropriate ???]
be rebound, as appropriate ???]
- 6.7.2. Setting Switches
6.7.2. Setting Switches
6.7.2. Setting Switches
- Strictly speaking, XXXX is a switch and !*XXXX is a corresponding global
- variable that assumes the T/NIL value; both are loosely referred to as
- switches elsewhere in the manual.
- On Off
On Off
The On and Off functions are used to change the values of the variables
- associated with switches. Some switches contain an s-expression on their
- 1
- property lists under the indicator 'SIMPFG . The s-expression has the form
- Cond
Cond
of a Cond list:
- ((T (action-for-ON)) (NIL (action-for-OFF)))
- On Off
On Off
If the 'SIMPFG indicator is present, then the On and Off functions also
- evaluate the appropriate action in the s-expression.
- On
On _ __ ____ _____
(On [U:id]): None macro
- _
For each U, the associated !*U variable is set to T. If a "(T
- GET
GET _
(action-for-ON))" clause is found by (GET U 'SIMPFG), the
- "action" is EVAL'ed.
- Off
Off _ __ ____ _____
(Off [U:id]): None macro
- _
For each U, the associated !*U variable is set to NIL. If a
- GET
GET _
"(NIL (action-for-OFF)" clause is found by (GET U 'SIMPFG), the
- "action" is EVAL'ed.
- (On Comp Ord Usermode)
- will set !*Comp, !*Ord, and !*Usermode to T.
- Note that
- _______________
- 1
- The name SIMPFG comes from its introduction in the REDUCE algebra
- system, where it was used as a "simp flag" to specify various
- simplifications to be performed as various switches were turned on or off.
PSL Manual 7 February 1983 Identifiers
- section 6.7 page 6.15
- (Get 'Cref 'Simpfg)
- returns
- ((T (Crefon)) (Nil (Crefoff)))
- ____ ____
Setting CREF on will result in !*CREF being set to T and the function
- Crefon
Crefon
Crefon being evaluated.
- 6.7.3. Special Global Variables
6.7.3. Special Global Variables
6.7.3. Special Global Variables
- __________ ______
NIL [Initially: NIL] global
- NIL is a special GLOBAL variable. It is protected from being
- Set SetQ
Set SetQ
modified by Set or SetQ.
- __________ ______
T [Initially: T] global
- T is a special GLOBAL variable. It is protected from being
- Set SetQ
Set SetQ
modified by Set or SetQ.
- 6.7.4. Special Put Indicators
6.7.4. Special Put Indicators
6.7.4. Special Put Indicators
- __
Some actions search the property list of relevant ids for these
- indicators:
- __
'HELPFUNCTION An id, a function to be executed to give help about the
- topic; ideally for a complex topic, a clever function is
- used.
- 'HELPSTRING A help string, kept in core for important or short topics.
- 'HELPFILE The most common case, the name of a file to print; later we
- hope to load this file into an EMODE buffer for perusal in a
- window.
- 'SWITCHINFO A string describing the purpose of the SWITCH, see
- ShowSwitches
ShowSwitches
ShowSwitches below.
- 'GLOBALINFO A string describing the purpose of the GLOBAL, see
- ShowGlobals
ShowGlobals
ShowGlobals below.
- __
'BREAKFUNCTION Associates a function to be run with an Id typed at Break
- Loop, see Chapter 14.
- 'TYPE PSL uses the property TYPE to indicate whether a function is
- a FEXPR, MACRO, or NEXPR; if no property is present, EXPR is
Identifiers 7 February 1983 PSL Manual
- page 6.16 section 6.7
- assumed.
- 'VARTYPE PSL uses the property VARTYPE to indicate whether an
- __________
identifier is of type GLOBAL or FLUID.
- '!*LAMBDALINK The interpreter also looks under '!*LAMBDALINK for a Lambda
- expression, if a procedure is not compiled.
- 6.7.5. Special Flag Indicators
6.7.5. Special Flag Indicators
6.7.5. Special Flag Indicators
- __
'EVAL If the id is flagged EVAL, the RLISP top-loop evaluates and
- On Defn
__ On Defn
outputs any expression (id ...) in On Defn (!*DEFN := T) mode.
- __
'IGNORE If the id is flagged IGNORE, the RLISP top-loop evaluates but
- On Defn
__ On Defn
does NOT output any expression (id ...) in On Defn (!*DEFN := T)
- mode.
- PutD
__ PutD
'LOSE If an id has the 'LOSE flag, it will not be defined by PutD when
- it is read in.
- 'USER 'USER is put on all functions defined when in !*USERMODE, to
- distinguish them from "system" functions. See Chapter 10.
- LoadTime CompileTime
LoadTime CompileTime
See also the functions LoadTime and CompileTime in Chapter 18.
- [??? Mention Parser properties ???]
[??? Mention Parser properties ???]
[??? Mention Parser properties ???]
- 6.7.6. Displaying Information About Globals
6.7.6. Displaying Information About Globals
6.7.6. Displaying Information About Globals
- Help
Help
The Help function has two options, (HELP SWITCHES) and (HELP GLOBALS),
- which should display the current state of a variety of switches and globals
- respectively. These calls have the same effect as using the functions
- below, using an initial table of Switches and Globals.
- ShowSwitches
ShowSwitches
The function (ShowSwitches switch-list) may be used to print names,
- current settings and purpose of some switches. Use NIL as the switch-list
- ShowSwitches
ShowSwitches
to get information on ALL switches of interest; ShowSwitches in this case
- MapObl
MapObl
does a MapObl (Section 6.3.1) looking for 'SwitchInfo property.
- ShowGlobals
ShowGlobals
Similarly, (ShowGlobals global-list) may be used to print names, values
- and purposes of important GLOBALs. Again, NIL used as the global-list
- ShowGlobals MapObl
ShowGlobals MapObl
causes ShowGlobals to do a MapObl looking for a 'GlobalInfo property; the
- result is some information about all globals of interest.
|
