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Tcl_ListObj(3)		    Tcl Library Procedures		Tcl_ListObj(3)

______________________________________________________________________________

NAME
       Tcl_ListObjAppendList,	  Tcl_ListObjAppendElement,    Tcl_NewListObj,
       Tcl_SetListObj, Tcl_ListObjGetElements, Tcl_ListObjLength,  Tcl_ListOb‐
       jIndex, Tcl_ListObjReplace - manipulate Tcl objects as lists

SYNOPSIS
       #include <tcl.h>

       int
       Tcl_ListObjAppendList(interp, listPtr, elemListPtr)

       int
       Tcl_ListObjAppendElement(interp, listPtr, objPtr)

       Tcl_Obj *
       Tcl_NewListObj(objc, objv)

       Tcl_SetListObj(objPtr, objc, objv)

       int
       Tcl_ListObjGetElements(interp, listPtr, objcPtr, objvPtr)

       int
       Tcl_ListObjLength(interp, listPtr, intPtr)

       int
       Tcl_ListObjIndex(interp, listPtr, index, objPtrPtr)

       int
       Tcl_ListObjReplace(interp, listPtr, first, count, objc, objv)

ARGUMENTS
       Tcl_Interp *interp (in)			 If an error occurs while con‐
						 verting an  object  to	 be  a
						 list object, an error message
						 is left in the	 interpreter's
						 result	 object	 unless interp
						 is NULL.

       Tcl_Obj *listPtr (in/out)		 Points to the list object  to
						 be  manipulated.   If listPtr
						 does not already point	 to  a
						 list  object, an attempt will
						 be made to convert it to one.

       Tcl_Obj *elemListPtr (in/out)		 For	Tcl_ListObjAppendList,
						 this  points to a list object
						 containing  elements  to   be
						 appended  onto listPtr.  Each
						 element of *elemListPtr  will
						 become	  a   new  element  of
						 listPtr.  If *elemListPtr  is
						 not NULL and does not already
						 point to a  list  object,  an
						 attempt  will be made to con‐
						 vert it to one.

       Tcl_Obj *objPtr (in)			 For Tcl_ListObjAppendElement,
						 points to the Tcl object that
						 will be appended to  listPtr.
						 For	Tcl_SetListObj,	  this
						 points to the Tcl object that
						 will  be  converted to a list
						 object	 containing  the  objc
						 elements  of the array refer‐
						 enced by objv.

       int *objcPtr (in)			 Points	 to   location	 where
						 Tcl_ListObjGetElements stores
						 the number of element objects
						 in listPtr.

       Tcl_Obj ***objvPtr (out)			 A  location where Tcl_ListOb‐
						 jGetElements stores a pointer
						 to  an	 array	of pointers to
						 the   element	 objects    of
						 listPtr.

       int objc (in)				 The  number  of  Tcl  objects
						 that	Tcl_NewListObj	  will
						 insert	  into	 a   new  list
						 object,  and	Tcl_ListObjRe‐
						 place	  will	 insert	  into
						 listPtr.  For Tcl_SetListObj,
						 the  number of Tcl objects to
						 insert into objPtr.

       Tcl_Obj *const objv[] (in)		 An  array  of	 pointers   to
						 objects.  Tcl_NewListObj will
						 insert these objects  into  a
						 new  list object and Tcl_Lis‐
						 tObjReplace will insert  them
						 into	an  existing  listPtr.
						 Each  object  will  become  a
						 separate list element.

       int *intPtr (out)			 Points	  to   location	 where
						 Tcl_ListObjLength stores  the
						 length of the list.

       int index (in)				 Index	of  the	 list  element
						 that Tcl_ListObjIndex	is  to
						 return.   The	first  element
						 has index 0.

       Tcl_Obj **objPtrPtr (out)		 Points	  to	place	 where
						 Tcl_ListObjIndex  is to store
						 a pointer  to	the  resulting
						 list element object.

       int first (in)				 Index	of  the	 starting list
						 element  that	Tcl_ListObjRe‐
						 place	is  to	replace.   The
						 list's	 first	 element   has
						 index 0.

       int count (in)				 The  number  of elements that
						 Tcl_ListObjReplace   is    to
						 replace.
_________________________________________________________________

DESCRIPTION
       Tcl  list  objects  have	 an  internal representation that supports the
       efficient indexing and appending.  The procedures described in this man
       page  are used to create, modify, index, and append to Tcl list objects
       from C code.

       Tcl_ListObjAppendList and Tcl_ListObjAppendElement both add one or more
       objects	to the end of the list object referenced by listPtr.  Tcl_Lis‐
       tObjAppendList appends each element of the list	object	referenced  by
       elemListPtr  while  Tcl_ListObjAppendElement  appends the single object
       referenced by objPtr.  Both procedures will convert the	object	refer‐
       enced  by  listPtr  to  a list object if necessary.  If an error occurs
       during conversion, both procedures return TCL_ERROR and leave an	 error
       message in the interpreter's result object if interp is not NULL.  Sim‐
       ilarly, if elemListPtr  does  not  already  refer  to  a	 list  object,
       Tcl_ListObjAppendList will attempt to convert it to one and if an error
       occurs during conversion, will return TCL_ERROR and leave an error mes‐
       sage  in	 the  interpreter's result object if interp is not NULL.  Both
       procedures invalidate any old string representation of listPtr and,  if
       it  was	converted  to a list object, free any old internal representa‐
       tion.  Similarly, Tcl_ListObjAppendList frees any old  internal	repre‐
       sentation  of  elemListPtr  if  it converts it to a list object.	 After
       appending each element in elemListPtr, Tcl_ListObjAppendList increments
       the element's reference count since listPtr now also refers to it.  For
       the same reason, Tcl_ListObjAppendElement increments objPtr's reference
       count.	If  no	error  occurs,	the two procedures return TCL_OK after
       appending the objects.

       Tcl_NewListObj and Tcl_SetListObj create a  new	object	or  modify  an
       existing	 object	 to  hold the objc elements of the array referenced by
       objv where each element is a pointer to a Tcl object.  If objc is  less
       than  or	 equal to zero, they return an empty object.  The new object's
       string representation is left invalid.  The  two	 procedures  increment
       the  reference counts of the elements in objc since the list object now
       refers to them.	The new list object  returned  by  Tcl_NewListObj  has
       reference count zero.

       Tcl_ListObjGetElements returns a count and a pointer to an array of the
       elements in a list object.  It returns the count by storing it  in  the
       address objcPtr.	 Similarly, it returns the array pointer by storing it
       in the address objvPtr.	The memory pointed to is managed  by  Tcl  and
       should  not be freed or written to by the caller. If the list is empty,
       0 is stored at objcPtr and NULL at objvPtr.  If listPtr is not  already
       a  list	object,	 Tcl_ListObjGetElements	 will attempt to convert it to
       one; if the conversion fails, it returns TCL_ERROR and leaves an	 error
       message in the interpreter's result object if interp is not NULL.  Oth‐
       erwise it returns TCL_OK after storing the count and array pointer.

       Tcl_ListObjLength returns the number of elements	 in  the  list	object
       referenced  by listPtr.	It returns this count by storing an integer in
       the address intPtr.  If the  object  is	not  already  a	 list  object,
       Tcl_ListObjLength  will attempt to convert it to one; if the conversion
       fails, it returns TCL_ERROR and leaves an error message in  the	inter‐
       preter's	 result	 object	 if  interp is not NULL.  Otherwise it returns
       TCL_OK after storing the list's length.

       The procedure Tcl_ListObjIndex returns a pointer to the object at  ele‐
       ment  index  in the list referenced by listPtr.	It returns this object
       by storing a pointer to it in the address objPtrPtr.  If	 listPtr  does
       not  already  refer  to a list object, Tcl_ListObjIndex will attempt to
       convert it to one; if the conversion fails, it  returns	TCL_ERROR  and
       leaves an error message in the interpreter's result object if interp is
       not NULL.  If the index is out of range, that is, index is negative  or
       greater than or equal to the number of elements in the list, Tcl_ListO‐
       bjIndex stores a NULL in objPtrPtr and returns  TCL_OK.	 Otherwise  it
       returns	TCL_OK after storing the element's object pointer.  The refer‐
       ence count for the list element is not incremented; the caller must  do
       that if it needs to retain a pointer to the element.

       Tcl_ListObjReplace  replaces  zero  or more elements of the list refer‐
       enced by listPtr with the objc objects in the array referenced by objv.
       If  listPtr  does  not  point to a list object, Tcl_ListObjReplace will
       attempt to convert it to one;  if  the  conversion  fails,  it  returns
       TCL_ERROR  and  leaves  an  error  message  in the interpreter's result
       object if interp is not	NULL.	Otherwise,  it	returns	 TCL_OK	 after
       replacing the objects.  If objv is NULL, no new elements are added.  If
       the argument first is zero or negative, it refers to the first element.
       If  first  is  greater  than  or equal to the number of elements in the
       list, then no elements are deleted; the new elements  are  appended  to
       the  list.  count gives the number of elements to replace.  If count is
       zero or negative then no elements are deleted;  the  new	 elements  are
       simply inserted before the one designated by first.  Tcl_ListObjReplace
       invalidates listPtr's old string representation.	 The reference	counts
       of  any elements inserted from objv are incremented since the resulting
       list now refers to them.	  Similarly,  the  reference  counts  for  any
       replaced objects are decremented.

       Because	Tcl_ListObjReplace  combines  both element insertion and dele‐
       tion, it can be used to implement a number  of  list  operations.   For
       example,	 the following code inserts the objc objects referenced by the
       array of object pointers objv just before the element index of the list
       referenced by listPtr:

	      result = Tcl_ListObjReplace(interp, listPtr, index, 0,
		      objc, objv);

       Similarly,  the	following  code appends the objc objects referenced by
       the array objv to the end of the list listPtr:

	      result = Tcl_ListObjLength(interp, listPtr, &length);
	      if (result == TCL_OK) {
		  result = Tcl_ListObjReplace(interp, listPtr, length, 0,
			  objc, objv);
	      }

       The count list elements starting at first  can  be  deleted  by	simply
       calling Tcl_ListObjReplace with a NULL objvPtr:

	      result = Tcl_ListObjReplace(interp, listPtr, first, count,
		      0, NULL);

SEE ALSO
       Tcl_NewObj, Tcl_DecrRefCount, Tcl_IncrRefCount, Tcl_GetObjResult

KEYWORDS
       append,	index,	insert,	 internal  representation,  length, list, list
       object, list type, object, object type, replace, string representation

Tcl				      8.0			Tcl_ListObj(3)
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