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Tcl_ListObj(3)			      Tcl Library Procedures			   Tcl_ListObj(3)

_________________________________________________________________________________________________

NAME
       Tcl_ListObjAppendList,  Tcl_ListObjAppendElement, Tcl_NewListObj, Tcl_SetListObj, Tcl_Lis-
       tObjGetElements, Tcl_ListObjLength, Tcl_ListObjIndex, 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 *elem-
						 ListPtr 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 contain-
						 ing 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_Lis-
						 tObjReplace  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
						 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_Lis-
						 tObjReplace  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_ListObjAppendList appends each  element  of
       the  list object referenced by elemListPtr while Tcl_ListObjAppendElement appends the sin-
       gle 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 proce-
       dures 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 con-
       version,  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 representation.
       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_ListOb-
       jAppendList 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 refer-
       ence 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_Lis-
       tObjGetElements 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 conver-
       sion  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 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_ListObjRe-
       place invalidates listPtr's old string representation.  The reference counts of	any  ele-
       ments  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_ListObjRe-
       place 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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