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 values 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 a value to be a list
value, an error message is
left in the interpreter's
result value unless interp is
NULL.
Tcl_Obj *listPtr (in/out) Points to the list value to
be manipulated. If listPtr
does not already point to a
list value, an attempt will
be made to convert it to one.
Tcl_Obj *elemListPtr (in/out) For Tcl_ListObjAppendList,
this points to a list value
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 value, an
attempt will be made to con‐
vert it to one.
Tcl_Obj *objPtr (in) For Tcl_ListObjAppendElement,
points to the Tcl value that
will be appended to listPtr.
For Tcl_SetListObj, this
points to the Tcl value that
will be converted to a list
value 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 values
in listPtr.
Tcl_Obj ***objvPtr (out) A location where Tcl_ListOb‐
jGetElements stores a pointer
to an array of pointers to
the element values of
listPtr.
int objc (in) The number of Tcl values that
Tcl_NewListObj will insert
into a new list value, and
Tcl_ListObjReplace will
insert into listPtr. For
Tcl_SetListObj, the number of
Tcl values to insert into
objPtr.
Tcl_Obj *const objv[] (in) An array of pointers to val‐
ues. Tcl_NewListObj will
insert these values into a
new list value and Tcl_ListO‐
bjReplace will insert them
into an existing listPtr.
Each value 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 value.
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 values have an internal representation that supports the effi‐
cient indexing and appending. The procedures described in this man
page are used to create, modify, index, and append to Tcl list values
from C code.
Tcl_ListObjAppendList and Tcl_ListObjAppendElement both add one or more
values to the end of the list value referenced by listPtr. Tcl_ListOb‐
jAppendList appends each element of the list value referenced by elem‐
ListPtr while Tcl_ListObjAppendElement appends the single value refer‐
enced by objPtr. Both procedures will convert the value referenced by
listPtr to a list value if necessary. If an error occurs during con‐
version, both procedures return TCL_ERROR and leave an error message in
the interpreter's result value if interp is not NULL. Similarly, if
elemListPtr does not already refer to a list value, Tcl_ListObjAp‐
pendList will attempt to convert it to one and if an error occurs dur‐
ing conversion, will return TCL_ERROR and leave an error message in the
interpreter's result value if interp is not NULL. Both procedures
invalidate any old string representation of listPtr and, if it was con‐
verted to a list value, free any old internal representation. Simi‐
larly, Tcl_ListObjAppendList frees any old internal representation of
elemListPtr if it converts it to a list value. After appending each
element in elemListPtr, Tcl_ListObjAppendList increments the element's
reference count since listPtr now also refers to it. For the same rea‐
son, Tcl_ListObjAppendElement increments objPtr's reference count. If
no error occurs, the two procedures return TCL_OK after appending the
values.
Tcl_NewListObj and Tcl_SetListObj create a new value or modify an
existing value to hold the objc elements of the array referenced by
objv where each element is a pointer to a Tcl value. If objc is less
than or equal to zero, they return an empty value. The new value's
string representation is left invalid. The two procedures increment
the reference counts of the elements in objc since the list value now
refers to them. The new list value returned by Tcl_NewListObj has ref‐
erence count zero.
Tcl_ListObjGetElements returns a count and a pointer to an array of the
elements in a list value. 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 value, Tcl_ListObjGetElements will attempt to convert it to one;
if the conversion fails, it returns TCL_ERROR and leaves an error mes‐
sage in the interpreter's result value if interp is not NULL. Other‐
wise it returns TCL_OK after storing the count and array pointer.
Tcl_ListObjLength returns the number of elements in the list value ref‐
erenced by listPtr. It returns this count by storing an integer in the
address intPtr. If the value is not already a list value, Tcl_ListOb‐
jLength 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 value 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 value at ele‐
ment index in the list referenced by listPtr. It returns this value by
storing a pointer to it in the address objPtrPtr. If listPtr does not
already refer to a list value, 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 value 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 value 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 refer‐
enced by listPtr with the objc values in the array referenced by objv.
If listPtr does not point to a list value, 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 value
if interp is not NULL. Otherwise, it returns TCL_OK after replacing
the values. If objv is NULL, no new elements are added. If the argu‐
ment 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 inval‐
idates 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 values 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 values referenced by the
array of value 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 values 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 ALSOTcl_NewObj(3), Tcl_DecrRefCount(3), Tcl_IncrRefCount(3), Tcl_GetObjRe‐
sult(3)KEYWORDS
append, index, insert, internal representation, length, list, list
value, list type, value, value type, replace, string representation
Tcl 8.0 Tcl_ListObj(3)
