tcl_listobj(3)

NAME

Tcl_ListObjAppendList, Tcl_ListObjAppendElement,
Tcl_NewListObj, Tcl_SetListObj, Tcl_ListObjGetElements,
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 manip
ulated. 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_ListObjAp: pendList, this points to a list
object containing
elements to be
appended onto
listPtr. Each ele ment of
*elemListPtr will become a new ele
ment 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_ListObjAp: pendElement, 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_ListOb jGetElements stores the number of ele
ment objects in
listPtr.
Tcl_Obj ***objvPtr (out) A location where: Tcl_ListObjGetEle ments 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_ListObjReplace will insert into
listPtr. For Tcl_SetListObj, the number of Tcl
objects to insert
into objPtr.
Tcl_Obj "*CONST objv[]" in: An array of point
ers 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_ListOb jLength 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_ListOb jIndex is to store a pointer to the
resulting list ele
ment object.
int first (in) Index of the start: ing list element
that Tcl_ListObjRe place is to
replace. The
list's first ele
ment has index 0.
int count (in) The number of ele: ments that Tcl_Lis tObjReplace is to replace.

DESCRIPTION

Tcl list objects have an internal representation that sup
ports the efficient indexing and appending. The proce
dures described in this man page are used to create, mod
ify, 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 ref
erenced by listPtr. Tcl_ListObjAppendList appends each element of the list object referenced by elemListPtr while Tcl_ListObjAppendElement appends the single object refer enced 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 elem_ ListPtr does not already refer to a list object, Tcl_Lis tObjAppendList 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 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_ListObjAppendList increments the element's reference count since listPtr now also refers to it. For the same reason, Tcl_ListObjAppendElement increments objPtr's ref erence 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 rep
resentation 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 by the caller. 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 num
ber 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 incre
mented; 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 ele
ments 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 desig
nated 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 refer
ence 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);

KEYWORDS

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

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