{Begin SubSec Type Number Functions}
{Title Type Number Functions}
{Text

{index type numbers}

Each data type in Interlisp has an associated "type name".  In Interlisp-10, each data type also has a "type number", which can be accessed and manipulated with the functions below.  In general, it is preferable to use the type name functions (see {PageRef Fn TYPENAME}).


{FnDef {FnName NTYP} {FnArgs DATUM}
{Text
Returns the type number for the data type of {arg DATUM}, e.g., {lisp (NTYP '(A . B))} is 8, the type number for lists.
}}


{FnDef {FnName TYPEP} {FnArgs DATUM N}
{Text
Value is {lisp T}, if the type number of {arg DATUM} is equal to {arg N}.
}}


{FnDef {FnName TYPENAMEFROMNUMBER} {FnArgs N}
{Text
Value is type name for type number {arg N}, or {lisp NIL} if {arg N} is not a valid type number, e.g. {lisp (TYPENAMEFROMNUMBER 30)}={lisp STRING.CHARS}.
}}


{FnDef {FnName TYPENUMBERFROMNAME} {FnArgs NAME}
{Text
Value is corresponding type number for {arg NAME}, or {lisp NIL} if {arg NAME} is not a type name, e.g. {lisp (TYPENUMBERFROMNAME 'STRING.CHARS)}={lisp 30}.

{fn TYPENUMBERFROMNAME} will accept {lisp READTABLEP}, {lisp TERMTABLEP}, {lisp CCODEP}, and {lisp ARRAYP}, and return the same value for each, which for Interlisp-10 is 1.  Note however that {lisp (TYPENAMEFROMNUMBER 1)}={lisp ARRAYP}.
}}



{FnDef {FnName GETTYPEDESCRIPTION} {FnArgs TYPE}
{Text
Returns the type description string for {arg TYPE}, a type name or type number.{index type description}
}}


{FnDef {FnName SETTYPEDESCRIPTION} {FnArgs TYPE STRING}
{Text 
Sets the type description string for {arg TYPE} to be {arg STRING}.  The type description is used in garbage collection messages and by {fn STORAGE}.{index type description}
}}



{Begin Note}
Date: 4 June 1981 1:31 pm PDT (Thursday)
From: Masinter.PA
Subject: machine dependent functions
To: LispDiscussion^

Principle: implementation-dependent functions which have different
behavior should not have the same name; this is to aid in converting
from one system to another. For example, Interlisp-D's
PUTBASE function deals with 16 bit quantities; thus Interlisp-Jericho
should not have a function with the same name which deals with
32 bit quantitites.

>  Interlisp-D internal functions ADDBASE, PUTBASE, etc.
   will be renamed with "\" to more readily identify them.

>  We will standardize a set of constants for internal datatype numbers
   including \FIXP, \FLOATP, \SMALLP, \LITATOM, \STRINGP,
   \ARRAYP, \STACKP. I propose the function (NTYPX) become an Interlisp
   standard which returns a type-number; the reason for renaming is
   so that old Interlisp-10 programs which contain explicit type numbers
   (rather than using constants) can be detected; in Interlisp-10 (and
   in Interlisp-Jericho) NTYPX = NTYP. I propose that TYPENAMEFROMNUMBER
   and TYPENUMBERFROMNAME become part of the Interlisp standard.
{End Note}




}{End SubSec Type Number Functions}