Tcl_ListObj(3)						      Tcl Library Procedures						    Tcl_ListObj(3)

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NAME

       Tcl_ListObjAppendList,  Tcl_ListObjAppendElement, Tcl_NewListObj, Tcl_SetListObj, Tcl_ListObjGetElements, Tcl_ListObjLength, Tcl_ListObjIn-
       dex, 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 converting 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  convert  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 referenced 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_ListObjGetElements 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_ListOb-
						 jReplace  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_ListObjReplace will insert them into an existing listPtr.  Each object will become a sep-
						 arate 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_ListObjReplace is to replace.  The list's first ele-
						 ment has index 0.

       int count (in)				 The number of elements that Tcl_ListObjReplace is to replace.
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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_ListObjAppendList 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 referenced 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.  Similarly, 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 message 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 repre-
       sentation.  Similarly, Tcl_ListObjAppendList frees any old internal representation 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.  Otherwise 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 interpreter'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 element 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_ListObjIndex stores a NULL in objPtrPtr and returns TCL_OK.	Otherwise it returns TCL_OK after storing the  element's  object  pointer.
       The reference 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 referenced 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 replac-
       ing 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 sim-
       ply 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 deletion, 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)