Tcl_ListObj(3) Tcl Library Procedures Tcl_ListObj(3)

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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.
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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)