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• File psl-1983/help/defstruct.hlp — part of check-in [eb17ceb7f6] at 2020-04-21 19:40:01 on branch master — Add Reduce 3.0 to the historical section of the archive, and some more
  files relating to version sof PSL from the early 1980s. Thanks are due to
  Paul McJones and Nelson Beebe for these, as well as to all the original
  authors.

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DEFSTRUCT - "Structure" definition facility.
--------------------------------------------

A more complete description, including examples, is in Defstruct.Doc.

Defstruct( name-and-options:{id,list}, [slot-descs:{id,list}] ): id    fexpr
	   ----------------  -- ----    ----------  -- ----	 --    -----
      Defines a record-structure data type.  A general call to defstruct
      looks like this: (in RLISP syntax)

	    defstruct( struct-name( option-1, option-2, ... ),
		       slot-description-1,
		       slot-description-2,
		       ...
		     );	    % (The name of the defined structure is returned.)

      where slot-descriptions are:

	    slot-name( default-init, slot-option-1, slot-option-2, ... )

      Option lists and default-init forms are optional and may be omitted.
      Some options have optional argument lists.

      A call to a Constructor macro has the form:

	    MakeThing( slot-name-1 value-expr-1,
		       slot-name-2 value-expr-2,
		       ... );

      The Alterant macro calls have a similar form:

	    AlterThing( thing,
		        slot-name-1 value-expr-1,
		        slot-name-2 value-expr-2,
		        ... );

      A call to a Creator macro has the form:

	    CreateThing( slot-value-1, slot-value-2, ... );


Structure Options and arguments:

      Structure macro renaming, arg of NIL to suppress macro definition.
	!:Constructor name	% Default: MakeThing
	!:Alterant name		% Default: AlterThing
	!:Predicate name	% Default: ThingP
	!:Creator name		% Default: CreateThing

      Common prefix on selector/depositor names.
	!:Prefix idOrString	% Dedfault: ""
	!:Prefix		% If no arg, Struct name is prefix.

      Inclusion of substructures.
	 !:Include structName	% Starts with slot defns of subtype.
	 !:IncludeInit initList % slot-name(default-init) list to merge
				% with default-init forms of subtype.

  Slot Options:

	!:Type typeId		% Asserts the type of the slot.

      Override selectors/depositors with user-supplied fns.
	!:UserGet		% fn name is [prefix]slot-name.
	!:UserPut		% fn name is Put[prefix]slot-name.


Miscellaneous functions on types:

DefstructP( NAME:id ): extra-boolean				        expr
	    ---- --    -------------					---- 
      is a predicate that returns non-NIL (the Defstruct definition) if NAME
      is a structured type which has been defined using Defstruct, or NIL if
      it is not.

DefstructType( S:struct ): id						expr
	       - ------    --						----
      returns the type name field of an instance of a structured type, or
      NIL if S cannot be a defstruct type.

SubTypeP( NAME1:id, NAME2:id ): boolean					expr
      	  ----- --  ----- --    -------					----
      returns true if NAME1 is a structured type which has been !:Included in
      the definition of structured type NAME2, possibly through intermediate
      structure definitions.  (In other words, the selectors of NAME1 can be
      applied to NAME2.)