reduce-historical/psl-1983/lpt/04-datatypes.lpt

PSL Manual                    7 February 1983                    Data Types
section 4.0                                                        page 4.1

                                 CHAPTER 4
                                 CHAPTER 4
                                 CHAPTER 4
                                DATA TYPES
                                DATA TYPES
                                DATA TYPES




     4.1. Data Types and Structures Supported in PSL  .  .  .  .  .     4.1
          4.1.1. Data Types.  .  .  .  .  .  .  .  .  .  .  .  .  .     4.1
          4.1.2. Other Notational Conventions.  .  .  .  .  .  .  .     4.4
          4.1.3. Structures.  .  .  .  .  .  .  .  .  .  .  .  .  .     4.4
     4.2. Predicates Useful with Data Types  .  .  .  .  .  .  .  .     4.5
          4.2.1. Functions for Testing Equality .  .  .  .  .  .  .     4.6
          4.2.2. Predicates for Testing the Type of an Object  .  .     4.7
          4.2.3. Boolean Functions  .  .  .  .  .  .  .  .  .  .  .     4.8
     4.3. Converting Data Types  .  .  .  .  .  .  .  .  .  .  .  .     4.9




4.1. Data Types and Structures Supported in PSL
4.1. Data Types and Structures Supported in PSL
4.1. Data Types and Structures Supported in PSL


4.1.1. Data Types
4.1.1. Data Types
4.1.1. Data Types

  Data objects in PSL are tagged with their type.  This means that the type
declarations  required  in many programming languages are not needed.  Some
functions are "generic" in that the result they return depends on the types
                                                    ____                ___
of the arguments.  A tagged PSL object is called an item,  and  has  a  tag
                                                     ____
field  (9 bits on the DEC-20, 5 bits on the VAX), an info field (18 bits on
the DEC-20, 27 bits on  the  VAX),  and  possibly  some  bits  for  garbage
                 ____
collection.  The info field is either immediate data or an index or address
                                               __
into some other structure (such as the heap or id space).  For the purposes
                        ____
of  input and output of items, an appropriate notation is used (see Chapter
12 for  full  details  on  syntax,  restrictions,  etc.).    More  explicit
implementation details can be found in Chapters 20 and 21.

  The  basic  data  types  supported in PSL and a brief indication of their
representations are described below.


_______           _______
integer       The integers are also called "fixed" numbers.  The  magnitude
                  _______
              of  integers  is essentially unrestricted if the "big number"
                                                                   _______
              module, BIG, is loaded (LOAD BIG).  The notation for integers
              is a sequence of digits in an appropriate radix (radix 10  is
              the  default, which can be overridden by a radix prefix, such
              as  2#,  8#,  16#   etc).      There   are   three   internal
                                       _______
              representations    of    integers,   chosen   to   suit   the
              implementation:


              ____               ______              ____    ____
              inum      A signed number fitting into info.   Inums  do  not
                        require  dynamic storage and are represented in the
Data Types                    7 February 1983                    PSL Manual
page 4.2                                                        section 4.1

                        same  form as machine integers.  (19 bit [-2^18 ...
                        2^18 - 1] on the DEC-20, 28 bit on the VAX.)
              ______           ____        _______
              fixnum    A full-word signed integer, allocated in the  heap.
                        (36  bit on the DEC-20, fitting into a register; 32
                        bit on the VAX.)  

                          [??? Do we need fixnums, and if yes  how  large
                          [??? Do we need fixnums, and if yes  how  large
                          [??? Do we need fixnums, and if yes  how  large
                          ???]
                          ???]
                          ???]

              ______              _______
              bignum    A  signed integer of arbitrary precision, allocated
                                       _______    ______
                        as a vector of integers.  Bignums are currently not
                        installed by default; to use them, do (LOAD BIG).


_____            ________  _____
float         A  floating  point  number,  allocated  in  the  heap.    The
                               _____
              precision   of   floats   is   determined   solely   by   the
              implementation, and is 72-bit double precision on the DEC-20,
                                                     _____
              64-bit on the VAX.  The notation for a float is a sequence of
              digits with the addition of a single floating point ( . ) and
              optional exponent  (E  <integer>).    (No  spaces  may  occur
              between  the  point  and  the  digits).  Radix 10 is used for
              representing the mantissa and the  exponent  of  dty(floating
              point) numbers.

__               __________     __        ____
id            An identifier (or id) is an item whose info field points to a
              five-item structure containing the print name, property cell,
              value  cell, function cell, and package cell.  This structure
                                                                 __
              is contained in the id space.  The notation for an id is  its
              print  name, an alphanumeric character sequence starting with
                                                           __
              a letter.  One always refers to a particular id by giving its
              print name.  When presented with an appropriate  print  name,
                                                   __
              the  PSL  reader  will find a unique id to associate with it.
                                                            __
              See Chapters 6 and 12 for more information on ids  and  their
                                                        __
              syntax.  NIL and T are treated as special ids in PSL.

____                            ____
pair          A  primitive  two-item  structure  which has a left and right
                                       ___ ________
              part.  A notation called dot-notation is used, with the form:
              (<left-part> . <right-part>).  The <left-part>  is  known  as
                  Car                                     Cdr
                  Car                                     Cdr
              the Car portion and the <right-part> as the Cdr portion.  The
                               ____
              parts may be any item.  (Spaces are used to resolve ambiguity
                   _____
              with floats; see Chapter 12).

______                                           ____      _______
vector        A  primitive  uniform structure of items; an integer index is
              used  to  access  random  values  in  the  structure.     The
                                         ______        ___ ____
              individual  elements  of a vector may be any item.  Access to
              ______
              vectors is by means of  functions  for  indexing,  sub-vector
              extraction and concatenation, defined in Section 8.3.  In the
                           ______                     ______
              notation for vectors, the elements of a vector are surrounded
                                   ____   ____       ____
              by square brackets: [item-0 item-1 ... item-n].

______                  ______          ______
string        A  packed vector (or byte vector) of characters; the elements
                        _______
              are small integers  representing  the  ASCII  codes  for  the
PSL Manual                    7 February 1983                    Data Types
section 4.1                                                        page 4.3

                                   ____
              characters  (usually inums).  The elements may be accessed by
              indexing, substring and concatenation functions,  defined  in
                              ______
              Chapter   8.    String  notation  consists  of  a  series  of
              characters enclosed in  double  quotes,  as  in  "THIS  IS  A
              STRING".  A quote is included by doubling it, as in "HE SAID,
                                      ______
              ""LISP""".      (Input  strings  may  cross  the  end-of-line
              boundary, but a warning is given.)   See  !*EOLINSTRINGOK  in
              chapter 12.

____ ______      ______                     ____
word-vector   A  vector  of  machine-sized  words,  used  to implement such
                        ______    ______
              things as fixnums,  bignums,  etc.    The  elements  are  not
                                 ____
              considered  to  be items, and are not examined by the garbage
              collector.  

                           ____ ______
                           ____ ______
                           ____ ______
                [???  The  word-vector  could  be   used   to   implement
                [???  The  word-vector  could  be   used   to   implement
                [???  The  word-vector  could  be   used   to   implement
                machine-code blocks on some machines. ???]
                machine-code blocks on some machines. ???]
                machine-code blocks on some machines. ???]

____ ______     ______                         ____ ______
Byte-Vector   A vector of bytes.  Internally a byte-vector is the same as a
              ______
              string, but it is printed differently as a vector of integers
              instead of characters.

________ ______
Halfword-Vector
                ______
              A vector of machine-sized halfwords.

____ _______        ____
code-pointer  This  item  is  used  to refer to the entry point of compiled
                         _____  ______  ______
                         _____  ______  ______
                         _____  ______  ______
                         exprs  fexprs  macros
                         exprs  fexprs  macros
              functions (exprs, fexprs, macros, etc.), permitting  compiled
              functions to be renamed, passed around anonymously, etc.  New
                                                             Lap Fasl
              ____ _______                                   Lap Fasl
              code-pointers  are  created  by  the  loader  (Lap,Fasl)  and
              associated functions.  They  can  be  printed;  the  printing
              function  prints  the number of arguments expected as well as
              the entry point.  The value appears in the convention of  the
              implementation (#<Code a nnnn> on the DEC-20 and VAX, where a
              is the number of arguments and nnnn is the entry point).

                                                                        ___
                                                                        ___
                                                                        ___
                                                                       [not
___ _______                                                            [not
env-pointer   A  data  type  used  to  support  a  funarg capability.  [not
              ___________ ___
              ___________ ___
              ___________ ___
              implemented yet]
              implemented yet]
              implemented yet]


4.1.2. Other Notational Conventions
4.1.2. Other Notational Conventions
4.1.2. Other Notational Conventions

  Certain functional arguments can be any  of  a  number  of  types.    For
convenience,  we  give  these commonly used sets a name.  We refer to these
sets as "classes" of primitive data  types.    In  addition  to  the  types
described  above and the names for classes of types given below, we use the
following conventions in the manual.  {XXX, YYY} indicates that either data
type XXX or data type YYY will do.  {XXX}-{YYY} indicates that  any  object
of  type  XXX  can be used except those of type YYY; in this case, YYY is a
                              _______   _____
subset of XXX.  For example, {integer,  float}  indicates  that  either  an
_______         _____                 ___   ______
integer  or  a  float is acceptable; {any}-{vector} means any type except a
______
vector.
Data Types                    7 February 1983                    PSL Manual
page 4.4                                                        section 4.1

___                                            _ __________
any            Any  of  the types given above. S-expression is another term
                   ___
               for any.  All PSL entities have some value unless  an  error
               occurs during evaluation.
____                      ___   ____
atom           The class {any}-{pair}.
_______
boolean        The  class of global variables {T, NIL}, or their respective
               values, {T, NIL}.  (See Chapter 6.7).
_________      _______
character      Integers in  the  range  of  0  to  127  representing  ASCII
               character  codes.   These are distinct from single-character
               __
               ids.
________                     _______  _____  ______  ______  ____ _______
constant       The class of {integer, float, string, vector, code-pointer}.
                                                                       Eval
                 ________                                              Eval
               A constant evaluates to itself (see the definition  of  Eval
               in Chapter 11).
_____ _______
extra-boolean  Any  value  in the system.  Anything that is not NIL has the
               _______
               boolean interpretation T.
_____                                                                   __
ftype          The class of definable function  types.    The  set  of  ids
                ____  _____  _____  _____
                ____  _____  _____  _____
                ____  _____  _____  _____
                expr  fexpr  macro  nexpr
                expr  fexpr  macro  nexpr
               {expr, fexpr, macro, nexpr}.
                    _____                           __________
               The  ftype  is  ONLY an attribute of identifiers, and is not
                                                         ____ _______
               associated with either executable  code  (code-pointers)  or
               ______
               lambda expressions.
__ _______             _______
io-channel     A small integer representing an io channel.
______                       _______  _____
number         The class of {integer, float}.
_ ______                     ______         ______  ______  ____ ______
x-vector       Any  kind  of vector; i.e. a string, vector, word-vector, or
               ____
               word.
_________
Undefined      An implementation-dependent value returned by some low-level
               functions; i.e. the user should not depend on this value.
____ ________
None Returned  A notational convenience used to indicate control  functions
               that  do not return directly to the calling point, and hence
                                             Go
                                             Go
               do not return a value.  (e.g. Go)


4.1.3. Structures
4.1.3. Structures
4.1.3. Structures

                                        ____    ____
  Structures are entities created using pairs.  Lists are  structures  very
                                                        ____
commonly  required  as  parameters  to functions.  If a list of homogeneous
                                                                  ____
entities is required by a function, this class is denoted by  xxx-list,  in
                                                                       ____
which  xxx is the name of a class of primitives or structures.  Thus a list
   __        __ ____    ____    _______        _______ ____
of ids is an id-list, a list of integers is an integer-list, and so on.


____        ____                                      ____  ___   ____
list      A list is recursively defined as NIL or the pair (any . list).  A
                                  ____ ________                      ____
          special notation called list-notation is used to represent lists.
          List-notation eliminates the extra parentheses and dots  required
          by   dot-notation,  as  illustrated  below.    List-notation  and
          dot-notation may be mixed, as  shown  in  the  second  and  third
          examples.  (See section 3.3.3.)


              ____________             _____________
              dot-notation             list-notation
              (a . (b . (c . NIL)))    (a b c)
              (a . (b . c))            (a b . c)
              (a . ((b . c) . (d . NIL)))
PSL Manual                    7 February 1983                    Data Types
section 4.1                                                        page 4.5

          Note: () is an alternate input representation of NIL.

_ ____        _ ____      ___________ ____
a-list    An  a-list,  or association list, is a list in which each element
                         Car
               ____      Car
          is a pair, the Car part being a key associated with the value  in
              Cdr
              Cdr
          the Cdr part.

____         ____
form      A  form  is  an S-expression (any) which is legally acceptable to
          Eval
          Eval
          Eval; that is, it is syntactically and semantically  accepted  by
          the  interpreter  or  the  compiler.    (See  Chapter 11 for more
          details.)

______
lambda    A lambda  expression  must  have  the  form  (in  list-notation):
                                                                 __ ____
          (LAMBDA  parameters  .    body).    "Parameters" is an id-list of
                                                    ____
          formal parameters for "body", which is a  form  to  be  evaluated
                               ProgN
                               ProgN
          (note  the  implicit ProgN).  The semantics of the evaluation are
                         Eval
                         Eval
          defined by the Eval function (see chapter 11).

________    ______       ____ _______
function  A lambda, or a code-pointer.  A function is always  evaluated  as
          Eval  Spread
          Eval  Spread
          Eval, Spread.



4.2. Predicates Useful with Data Types
4.2. Predicates Useful with Data Types
4.2. Predicates Useful with Data Types

  Most  functions  in this Section return T if the condition defined is met
and NIL if it is not.  Exceptions are noted.    Defined  are  type-checking
functions and elementary comparisons.


4.2.1. Functions for Testing Equality
4.2.1. Functions for Testing Equality
4.2.1. Functions for Testing Equality

  Functions  for  testing  equality  are listed below.  For other functions
comparing arithmetic values see Chapter 5.


 Eq
 Eq _ ___   _ ___   _______                             ____ ________  ____
(Eq U:any   V:any): boolean                             open-compiled, expr

                  _                              _
     Returns T if U points to the same object as V, i.e. if  they  are
                       Eq
               ____    Eq    ___
     identical items.  Eq is not a reliable comparison between numeric
     arguments.    This  function  should  only  be  used  in  special
                                                                Equal
                                                                Equal
     circumstances.  Normally, equality should be tested  with  Equal,
     described below.


 EqN
 EqN _ ___   _ ___   _______                                           ____
(EqN U:any   V:any): boolean                                           expr

                                 Eq
                     _     _     Eq       _     _
     Returns  T  if  U and V are Eq or if U and V are numbers and have
     the same value and type.  

       [??? Should numbers of different type be EqN?  e.g. 0 vs. 0.0
       [??? Should numbers of different type be EqN?  e.g. 0 vs. 0.0
       [??? Should numbers of different type be EqN?  e.g. 0 vs. 0.0
       ???]
       ???]
       ???]
Data Types                    7 February 1983                    PSL Manual
page 4.6                                                        section 4.2

 Equal
 Equal _ ___   _ ___   _______                                         ____
(Equal U:any   V:any): boolean                                         expr

                     _       _                     ____
     Returns  T  if  U  and  V  are  the  same.    Pairs  are compared
                                                         ______
     recursively to the bottom levels of their trees.    Vectors  must
                                       Equal
                                       Equal
     have  identical  dimensions  and  Equal  values in all positions.
     ______
     Strings must have identical characters, i.e. all characters  must
                                                     Eq
                             ____ _______            Eq
     be  of  the same case.  Code-pointers must have Eq values.  Other
                   Eqn
     ____          Eqn
     atoms must be Eqn equal.  A usually valid heuristic  is  that  if
                                                                Print
                                                                Print
     two  objects  look  the  same if printed with the function Print,
              Equal                                           Equal
              Equal                                     ____  Equal
     they are Equal.  If one argument is known to be an atom, Equal is
                      Eq
                      Eq
     open-compiled as Eq.

         For example, if
             (Setq X '(A B C)) and (Setq Y X) have been executed, then
             (EQ X Y) is T
             (EQ X '(A B C)) is NIL
             (EQUAL X '(A B C)) is T
             (EQ 1 1) is T
             (EQ 1.0 1.0) is NIL
             (EQN 1.0 1.0) is T
             (EQN 1 1.0) is NIL
             (EQUAL 0 0.0) is NIL


 Neq
 Neq _ ___   _ ___   _______                                          _____
(Neq U:any   V:any): boolean                                          macro

      Not  Equal
      Not  Equal _ _
     (Not (Equal U V)).


 Ne
 Ne _ ___   _ ___   _______                             ____ ________  ____
(Ne U:any   V:any): boolean                             open-compiled, expr

      Not  Eq
      Not  Eq _ _
     (Not (Eq U V)).


 EqStr
 EqStr _ ___   _ ___   _______                                         ____
(EqStr U:any   V:any): boolean                                         expr

                 ______
     Compare two strings, for exact (Case sensitive)  equality.    For
     case-INsensitive  equality  one must load the STRINGS module (see
                    EqStr                          Eq
                    EqStr              _     _     Eq        _       _
     Section 8.7).  EqStr returns T if U and V are Eq or if  U  and  V
     are equal strings.


 EqCar
 EqCar _ ___   _ ___   _______                                         ____
(EqCar U:any   V:any): boolean                                         expr

                      Eq   Car
                      Eq   Car _  _
     Tests  whether  (Eq  (Car U) V)).  If the first argument is not a
           EqCar
           EqCar
     pair, EqCar returns NIL.
PSL Manual                    7 February 1983                    Data Types
section 4.2                                                        page 4.7

4.2.2. Predicates for Testing the Type of an Object
4.2.2. Predicates for Testing the Type of an Object
4.2.2. Predicates for Testing the Type of an Object


 Atom
 Atom _ ___   _______                                   ____ ________  ____
(Atom U:any): boolean                                   open-compiled, expr

                  _          ____
     Returns T if U is not a pair.


 CodeP
 CodeP _ ___   _______                                  ____ ________  ____
(CodeP U:any): boolean                                  open-compiled, expr

                  _      ____ _______
     Returns T if U is a code-pointer.


 ConstantP
 ConstantP _ ___   _______                                             ____
(ConstantP U:any): boolean                                             expr

                  _      ________                     ____        __
     Returns T if U is a constant (that is, neither a pair nor an id).
               ______                 ________
     Note that vectors are considered constants.

       [??? Should Eval U Eq U if U is a constant? ???]
       [??? Should Eval U Eq U if U is a constant? ???]
       [??? Should Eval U Eq U if U is a constant? ???]


 FixP
 FixP _ ___   _______                                   ____ ________  ____
(FixP U:any): boolean                                   open-compiled, expr

                     _       _______
     Returns  T  if  U is an integer.  If BIG is loaded, this function
     also returns T for bignums.


 FloatP
 FloatP _ ___   _______                                 ____ ________  ____
(FloatP U:any): boolean                                 open-compiled, expr

                  _      _____
     Returns T if U is a float.


 IdP
 IdP _ ___   _______                                    ____ ________  ____
(IdP U:any): boolean                                    open-compiled, expr

                  _       __
     Returns T if U is an id.


 Null
 Null _ ___   _______                                   ____ ________  ____
(Null U:any): boolean                                   open-compiled, expr

                                                                  Not
                  _                                               Not
     Returns T if U is NIL.  This is exactly the same function as Not,
     defined in Section 4.2.3.  Both are available solely to  increase
     readability.  


 NumberP
 NumberP _ ___   _______                                ____ ________  ____
(NumberP U:any): boolean                                open-compiled, expr

                  _      ______  _______    _____
     Returns T if U is a number (integer or float).
Data Types                    7 February 1983                    PSL Manual
page 4.8                                                        section 4.2

 PairP
 PairP _ ___   _______                                  ____ ________  ____
(PairP U:any): boolean                                  open-compiled, expr

                  _      ____
     Returns T if U is a pair.


 StringP
 StringP _ ___   _______                                ____ ________  ____
(StringP U:any): boolean                                open-compiled, expr

                  _      ______
     Returns T if U is a string.


 VectorP
 VectorP _ ___   _______                                ____ ________  ____
(VectorP U:any): boolean                                open-compiled, expr

                  _      ______
     Returns T if U is a vector.


4.2.3. Boolean Functions
4.2.3. Boolean Functions
4.2.3. Boolean Functions

  Boolean functions return NIL for "false"; anything non-NIL is taken to be
true,  although a conventional way of representing truth is as T. Note that
T always evaluates to itself.  NIL may also be represented  as  '().    The
                  And  Or      Not
                  And  Or      Not
Boolean functions And, Or, and Not can be applied to any LISP type, and are
                          And     Or
                          And     Or
not  bitwise  functions.  And and Or are frequently used in LISP as control
structures as well as Boolean connectives (see Section 9.2).  For  example,
the following two constructs will give the same result:  

   (COND ((AND A B C) D))

   (AND A B C D)

Since  there  is  no  specific  Boolean  type  in LISP and since every LISP
expression has a value which may be used freely in conditionals,  there  is
no  hard  and  fast distinction between an arbitrary function and a Boolean
function.  However, the three functions presented here are by far the  most
useful in constructing more complex tests from simple predicates.


 Not
 Not _ ___   _______                                    ____ ________  ____
(Not U:any): boolean                                    open-compiled, expr

                     _
     Returns  T  if  U  is  NIL.  This is exactly the same function as
     Null
     Null
     Null, defined in Section 4.2.2.  Both  are  available  solely  to
     increase readability.


 And
 And  _ ____    _____ _______                          ____ ________  _____
(And [U:form]): extra-boolean                          open-compiled, fexpr

     And
     And                 _
     And  evaluates each U until a value of NIL is found or the end of
         ____
     the list is encountered.  If a non-NIL value is the  last  value,
                                                            And
                                                            And
     it  is returned; otherwise NIL is returned.  Note that And called
     with zero arguments returns T.
PSL Manual                    7 February 1983                    Data Types
section 4.2                                                        page 4.9

 Or
 Or  _ ____    _____ _______                           ____ ________  _____
(Or [U:form]): extra-boolean                           open-compiled, fexpr

     _
     U  is  any  number of expressions which are evaluated in order of
     their appearance.  If one is found to be non-NIL, it is  returned
                      Or
                      Or
     as  the value of Or.  If all are NIL, NIL is returned.  Note that
        Or
        Or
     if Or is called with zero arguments, it returns NIL.



4.3. Converting Data Types
4.3. Converting Data Types
4.3. Converting Data Types

  The following functions are used in converting data items from  one  type
to  another.    They  are  grouped according to the type returned.  Numeric
                                               Fix     Float
                                               Fix     Float
types may be converted using functions such as Fix and Float, described  in
Section 5.2.


 Intern
 Intern _  __ ______    __                                             ____
(Intern U:{id,string}): id                                             expr

                                 Intern
               ______      __    Intern              __ ____ _____
     Converts  string  to  id.   Intern searches the id-hash-table (or
             __ ____ _____                                          __
     current id-hash-table if the package system is loaded) for an  id
                                       _                     __
     with  the  same  print  name  as  U  and  returns  the  id on the
     __ ____ _____
     id-hash-table if a  match  is  found.    (See  Chapter  6  for  a
                       __ ____ _____
     discussion of the id-hash-table. Any properties and GLOBAL values
                                      _               _
     associated  with  the uninterned U are lost.  If U does not match
                                                       _
     any entry, a new one is created and returned.  If U has more than
     the maximum number of characters permitted by the  implementation
     (???), an error is signalled:  

     ***** Too many characters to INTERN 

       [??? Rewrite for package system; include search path, global,
       [??? Rewrite for package system; include search path, global,
       [??? Rewrite for package system; include search path, global,
       local, intern, etc.  See Chapter 6. ???]
       local, intern, etc.  See Chapter 6. ???]
       local, intern, etc.  See Chapter 6. ???]

     The maximum number of characters in any token is 5000.


 NewId
 NewId _ ______   __                                                   ____
(NewId S:string): id                                                   expr

                                    __               _____ ____
     Allocates  a  new  uninterned  id, and sets its print-name to the
     ______ _       ______    ___
     string S.  The string is not copied.

        (Setq New (NewId "NEWONE")) returns  NEWONE

                                             __
     Note that if one refers directly to the id NEWONE, it will become
     interned and a new position in the id space will be allocated  to
                                          __                        __
     it.    One  has  to refer to the new id indirectly through the id
     New.
Data Types                    7 February 1983                    PSL Manual
page 4.10                                                       section 4.3

 Int2Id
 Int2Id _ _______   __                                                 ____
(Int2Id I:integer): id                                                 expr

                   _______       __                     _    __
     Converts  an  integer to an id; this refers to the I'th id in the
                                                                Int2Id
     __                                                         Int2Id
     id space.  Since 0 ... 127 correspond to ASCII characters, Int2Id
     with an argument in this range converts  an  ASCII  code  to  the
                                    __
     corresponding single character id.

        (Int2Id 250)  returns QUOTIENT


 Id2Int
 Id2Int _ __   _______                                                 ____
(Id2Int D:id): integer                                                 expr

                 __                   _           _______
     Returns the id space position of D as a LISP integer.

        (Id2Int 'String) returns 182


 Id2String
 Id2String _ __   ______                                               ____
(Id2String D:id): string                                               expr

                               Id2String             Print
                    __         Id2String             Print
     Get  name from id space.  Id2String returns the Print name of its
                   ______
     argument as a string.    This  is  not  a  copy,  so  destructive
                                                            CopyString
                                                            CopyString
     operations should not be performed on the result.  See CopyString
     in Chapter 8.  

       [??? Should it be a copy? ???]
       [??? Should it be a copy? ???]
       [??? Should it be a copy? ???]

        (Id2String 'String)  returns "STRING"


 String2List
 String2List _ ______   ____ ____                                      ____
(String2List S:string): inum-list                                      expr

                          Length  Add1  Size
                 ____     Length  Add1  Size _
     Creates  a  list  of Length (Add1 (Size S)), converting the ASCII
                           _______
     characters into small integers.

       [??? What of 0/1 base for length vs length -1.  What  of  the
       [??? What of 0/1 base for length vs length -1.  What  of  the
       [??? What of 0/1 base for length vs length -1.  What  of  the
       NUL char added ???]
       NUL char added ???]
       NUL char added ???]

        (String2List "STRING")  returns (83 84 82 73 78 71)


 List2String
 List2String _ ____ ____   ______                                      ____
(List2String L:inum-list): string                                      expr

                                      Size
                   ______             Size    _               ____
     Allocates  a  string of the same Size as L, and converts inums to
                                                    ____
     characters according to their ASCII code.  The inums must  be  in
     the range 0 ... 127.  

       [??? Check if 0 ... 127, and signal error ???]
       [??? Check if 0 ... 127, and signal error ???]
       [??? Check if 0 ... 127, and signal error ???]

        (List2String '(83 84 82 73 78 71))  returns "STRING"
PSL Manual                    7 February 1983                    Data Types
section 4.3                                                       page 4.11

 String
 String  _ ____    ______                                             _____
(String [I:inum]): string                                             nexpr

                           ______                    ____
     Creates and returns a string containing all the inums given.

        (String 83 84 82 73 78 71)  returns "STRING"


 Vector
 Vector  _ ___    ______                                              _____
(Vector [U:any]): vector                                              nexpr

                           ______                    _
     Creates and returns a vector containing all the Us given.

        (Setq X (Vector 83 84 82 73 78 71))  returns
         [83 84 82 73 78 71]


 Vector2String
 Vector2String _ ______   ______                                       ____
(Vector2String V:vector): string                                       expr

                      _______         ______        ______
     Pack  the  small integers in the vector into a string of the same
     Size
     Size            _______
     Size, using the integers as ASCII values.

       [??? check for integer in range 0 ... 127 ???]
       [??? check for integer in range 0 ... 127 ???]
       [??? check for integer in range 0 ... 127 ???]

        (Vector2String X)  where X is defined as above returns
               "STRING"


 String2Vector
 String2Vector _ ______   ______                                       ____
(String2Vector S:string): vector                                       expr

                                                 Size
                ______        ______             Size
     Unpack the string into a vector of the same Size.   The  elements
              ______
     of  the  vector are small integers, representing the ASCII values
                          _
     of the characters in S.

        (String2Vector "VECTOR") returns [V E C T O R]


 Vector2List
 Vector2List _ ______   ____                                           ____
(Vector2List V:vector): list                                           expr

                               Size                Length  Upbv
              ____             Size    _           Length  Upbv _
     Create a list of the same Size as V (i.e. of  Length  Upbv(V)+1),
                                              Upbv
                                              Upbv _
     copying the elements in order 0, 1, ..., Upbv(V).

        (Vector2List [L I S T])  returns (L I S T)


 List2Vector
 List2Vector _ ____   ______                                           ____
(List2Vector L:list): vector                                           expr

                                                             Size
                              ____        ______             Size
     Copy the elements of the list into a vector of the same Size.

        (List2Vector '(V E C T O R)) returns [V E C T O R]