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Tcl_ListObjAppendElement(3) - Tcl_ListObjAppendElement, Tcl_ListObjAppendList, Tcl_ListObjGetElements, Tcl_ListObjIndex, Tcl_ListObjLength, Tcl_ListObjReplace, Tcl_NewListObj, Tcl_SetListObj - manipulate Tcl objects as lists - man 3 Tcl_ListObjAppendElement

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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_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(1,8))      If  an  error(8,n)  occurs while con-
                                              verting an object to be  a  list
                                              object, an error(8,n) message is left
                                              in(1,8)  the   interpreter's   result
                                              object unless interp is NULL.

       Tcl_Obj      *listPtr        (in(1,8)/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(1,8)/out)  For  Tcl_ListObjAppendList, this
                                              points to a list object contain-
                                              ing elements to be appended onto
                                              listPtr.  Each element of *elem-
                                              ListPtr  will  become a new ele-
                                              ment  of  listPtr.   If   *elem-
                                              ListPtr 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(1,8))      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 con-
                                              taining the objc elements of the
                                              array referenced by objv.

       int          *objcPtr        (in(1,8))      Points    to    location   where
                                              Tcl_ListObjGetElements    stores
                                              the number of element objects in(1,8)
                                              listPtr.

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

       int          objc            (in(1,8))      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(1,8)                                         ||
                                              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(1,8))      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_ListO-
                                              bjIndex is to store a pointer to
                                              the   resulting   list   element
                                              object.

       int          first           (in(1,8))      Index of the starting list  ele-
                                              ment  that Tcl_ListObjReplace is
                                              to replace.   The  list's  first
                                              element has index 0.

       int          count           (in(1,8))      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(1,8) this man(1,5,7)
       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(3,n) necessary.  If an error(8,n) occurs
       during conversion, both procedures return TCL_ERROR and leave an  error(8,n)
       message in(1,8) the interpreter's result object if(3,n) interp is not NULL.  Sim-
       ilarly, if(3,n) elemListPtr  does  not  already  refer  to  a  list  object,
       Tcl_ListObjAppendList will attempt to convert it to one and if(3,n) an error(8,n)
       occurs during conversion, will return TCL_ERROR and leave an error(8,n) mes-
       sage  in(1,8)  the  interpreter's result object if(3,n) interp is not NULL.  Both
       procedures invalidate any old string(3,n) representation of listPtr and,  if(3,n)
       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(3,n)  it converts it to a list object.  After
       appending each element in(1,8) 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(8,n)  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(1,3)
       than  or  equal to zero, they return an empty object.  The new object's
       string(3,n) representation is left invalid.  The  two  procedures  increment
       the  reference counts of the elements in(1,8) 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(1,8) a list object.  It returns the count by storing it  in(1,8)  the
       address objcPtr.  Similarly, it returns the array pointer by storing it
       in(1,8) the address objvPtr.  The memory pointed to is managed  by  Tcl  and
       should  not  be  freed by the caller.  If listPtr is not already a list
       object, Tcl_ListObjGetElements will attempt to convert it  to  one;  if(3,n)
       the  conversion fails, it returns TCL_ERROR and leaves an error(8,n) message
       in(1,8) the interpreter's result object if(3,n) interp is not NULL.  Otherwise it
       returns TCL_OK after storing the count and array pointer.

       Tcl_ListObjLength  returns  the  number  of elements in(1,8) the list object
       referenced by listPtr.  It returns this count by storing an integer  in(1,8)
       the  address  intPtr.   If  the  object  is  not already a list object,
       Tcl_ListObjLength will attempt to convert it to one; if(3,n) the  conversion
       fails,  it  returns TCL_ERROR and leaves an error(8,n) message in(1,8) the inter-
       preter's result object if(3,n) 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(1,8) the list referenced by listPtr.  It returns  this  object
       by  storing  a pointer to it in(1,8) the address objPtrPtr.  If listPtr does
       not already refer to a list object, Tcl_ListObjIndex  will  attempt  to
       convert  it  to  one; if(3,n) the conversion fails, it returns TCL_ERROR and
       leaves an error(8,n) message in(1,8) the interpreter's result object if(3,n) 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(1,8) the list, Tcl_ListO-
       bjIndex  stores  a  NULL in(1,8) 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(3,n) 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(1,8) the array referenced by objv.
       If listPtr does not point to a  list  object,  Tcl_ListObjReplace  will
       attempt  to  convert  it  to  one;  if(3,n) the conversion fails, it returns
       TCL_ERROR and leaves an  error(8,n)  message  in(1,8)  the  interpreter's  result
       object  if(3,n)  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(1,8)  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(3,n) 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(3,n) (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(3,n) representation



Tcl                                   8.0                       Tcl_ListObj(3)

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