Tcl_ListObj(3) Tcl Library Procedures Tcl_ListObj(3) ________________________________________________________________________________
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(3), Tcl_DecrRefCount(3), Tcl_IncrRefCount(3),
Tcl_GetObjResult(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)
tcl 8.6.13 - Generated Sun Jan 8 15:30:30 CST 2023