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)
