Provided by: tcl8.6-doc_8.6.13+dfsg-2_all 
NAME
Tcl_ListObjAppendList, Tcl_ListObjAppendElement, Tcl_NewListObj, Tcl_SetListObj,
Tcl_ListObjGetElements, Tcl_ListObjLength, Tcl_ListObjIndex, 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, lengthPtr)
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 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 convert 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
referenced 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_ListObjGetElements 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 values. Tcl_NewListObj
will insert these values into a new list value
and Tcl_ListObjReplace will insert them into an
existing listPtr. Each value will become a
separate list element.
int *lengthPtr (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_ListObjReplace 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 efficient 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_ListObjAppendList appends each element of
the list value referenced by elemListPtr while Tcl_ListObjAppendElement appends the single
value referenced by objPtr. Both procedures will convert the value referenced by listPtr
to a list value if necessary. If an error occurs during conversion, 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_ListObjAppendList 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
value if interp is not NULL. Both procedures invalidate any old string representation of
listPtr and, if it was converted to a list value, free any old internal representation.
Similarly, 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 reason, 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. If objv is
NULL, the resulting list contains 0 elements, with reserved space in an internal
representation for objc more elements (to avoid its reallocation later). 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 reference 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 message in the interpreter's result value 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 value referenced by listPtr.
It returns this count by storing an integer in the address lengthPtr. If the value is not
already a list value, 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 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 element 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 referenced 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 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 values 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
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 ALSO
Tcl_NewObj(3tcl), Tcl_DecrRefCount(3tcl), Tcl_IncrRefCount(3tcl), Tcl_GetObjResult(3tcl)
KEYWORDS
append, index, insert, internal representation, length, list, list value, list type,
value, value type, replace, string representation