1Tcl_ListObj(3)              Tcl Library Procedures              Tcl_ListObj(3)
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5______________________________________________________________________________
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NAME

8       Tcl_ListObjAppendList,     Tcl_ListObjAppendElement,    Tcl_NewListObj,
9       Tcl_SetListObj, Tcl_ListObjGetElements, Tcl_ListObjLength,  Tcl_ListOb‐
10       jIndex, Tcl_ListObjReplace - manipulate Tcl values as lists
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SYNOPSIS

13       #include <tcl.h>
14
15       int
16       Tcl_ListObjAppendList(interp, listPtr, elemListPtr)
17
18       int
19       Tcl_ListObjAppendElement(interp, listPtr, objPtr)
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21       Tcl_Obj *
22       Tcl_NewListObj(objc, objv)
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24       Tcl_SetListObj(objPtr, objc, objv)
25
26       int
27       Tcl_ListObjGetElements(interp, listPtr, objcPtr, objvPtr)
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29       int
30       Tcl_ListObjLength(interp, listPtr, intPtr)
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32       int
33       Tcl_ListObjIndex(interp, listPtr, index, objPtrPtr)
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35       int
36       Tcl_ListObjReplace(interp, listPtr, first, count, objc, objv)
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ARGUMENTS

39       Tcl_Interp *interp (in)                   If an error occurs while con‐
40                                                 verting a value to be a  list
41                                                 value,  an  error  message is
42                                                 left in the interpreter's re‐
43                                                 sult  value  unless interp is
44                                                 NULL.
45
46       Tcl_Obj *listPtr (in/out)                 Points to the list  value  to
47                                                 be  manipulated.   If listPtr
48                                                 does not already point  to  a
49                                                 list  value,  an attempt will
50                                                 be made to convert it to one.
51
52       Tcl_Obj *elemListPtr (in/out)             For    Tcl_ListObjAppendList,
53                                                 this  points  to a list value
54                                                 containing elements to be ap‐
55                                                 pended  onto  listPtr.   Each
56                                                 element of *elemListPtr  will
57                                                 become   a   new  element  of
58                                                 listPtr.  If *elemListPtr  is
59                                                 not NULL and does not already
60                                                 point to a list value, an at‐
61                                                 tempt will be made to convert
62                                                 it to one.
63
64       Tcl_Obj *objPtr (in)                      For Tcl_ListObjAppendElement,
65                                                 points  to the Tcl value that
66                                                 will be appended to  listPtr.
67                                                 For    Tcl_SetListObj,   this
68                                                 points to the Tcl value  that
69                                                 will  be  converted to a list
70                                                 value containing the objc el‐
71                                                 ements  of  the  array refer‐
72                                                 enced by objv.
73
74       int *objcPtr (in)                         Points  to   location   where
75                                                 Tcl_ListObjGetElements stores
76                                                 the number of element  values
77                                                 in listPtr.
78
79       Tcl_Obj ***objvPtr (out)                  A  location where Tcl_ListOb‐
80                                                 jGetElements stores a pointer
81                                                 to  an  array  of pointers to
82                                                 the   element    values    of
83                                                 listPtr.
84
85       int objc (in)                             The number of Tcl values that
86                                                 Tcl_NewListObj  will   insert
87                                                 into  a  new  list value, and
88                                                 Tcl_ListObjReplace  will  in‐
89                                                 sert   into   listPtr.    For
90                                                 Tcl_SetListObj, the number of
91                                                 Tcl values to insert into ob‐
92                                                 jPtr.
93
94       Tcl_Obj *const objv[] (in)                An array of pointers to  val‐
95                                                 ues.  Tcl_NewListObj will in‐
96                                                 sert these values into a  new
97                                                 list value and Tcl_ListObjRe‐
98                                                 place will insert  them  into
99                                                 an  existing  listPtr.   Each
100                                                 value will become a  separate
101                                                 list element.
102
103       int *intPtr (out)                         Points   to   location  where
104                                                 Tcl_ListObjLength stores  the
105                                                 length of the list.
106
107       int index (in)                            Index  of  the  list  element
108                                                 that Tcl_ListObjIndex  is  to
109                                                 return.   The  first  element
110                                                 has index 0.
111
112       Tcl_Obj **objPtrPtr (out)                 Points   to    place    where
113                                                 Tcl_ListObjIndex  is to store
114                                                 a pointer  to  the  resulting
115                                                 list element value.
116
117       int first (in)                            Index  of  the  starting list
118                                                 element  that  Tcl_ListObjRe‐
119                                                 place  is  to  replace.   The
120                                                 list's first element has  in‐
121                                                 dex 0.
122
123       int count (in)                            The  number  of elements that
124                                                 Tcl_ListObjReplace is to  re‐
125                                                 place.
126______________________________________________________________________________
127
128

DESCRIPTION

130       Tcl list values have an internal representation that supports the effi‐
131       cient indexing and appending.  The procedures  described  in  this  man
132       page  are  used to create, modify, index, and append to Tcl list values
133       from C code.
134
135       Tcl_ListObjAppendList and Tcl_ListObjAppendElement both add one or more
136       values to the end of the list value referenced by listPtr.  Tcl_ListOb‐
137       jAppendList appends each element of the list value referenced by  elem‐
138       ListPtr  while Tcl_ListObjAppendElement appends the single value refer‐
139       enced by objPtr.  Both procedures will convert the value referenced  by
140       listPtr  to  a list value if necessary.  If an error occurs during con‐
141       version, both procedures return TCL_ERROR and leave an error message in
142       the  interpreter's  result  value if interp is not NULL.  Similarly, if
143       elemListPtr does not already refer  to  a  list  value,  Tcl_ListObjAp‐
144       pendList  will attempt to convert it to one and if an error occurs dur‐
145       ing conversion, will return TCL_ERROR and leave an error message in the
146       interpreter's  result value if interp is not NULL.  Both procedures in‐
147       validate any old string representation of listPtr and, if it  was  con‐
148       verted  to  a  list value, free any old internal representation.  Simi‐
149       larly, Tcl_ListObjAppendList frees any old internal  representation  of
150       elemListPtr  if  it  converts it to a list value.  After appending each
151       element in elemListPtr, Tcl_ListObjAppendList increments the  element's
152       reference count since listPtr now also refers to it.  For the same rea‐
153       son, Tcl_ListObjAppendElement increments objPtr's reference count.   If
154       no  error  occurs, the two procedures return TCL_OK after appending the
155       values.
156
157       Tcl_NewListObj and Tcl_SetListObj create a new value or modify  an  ex‐
158       isting  value to hold the objc elements of the array referenced by objv
159       where each element is a pointer to a Tcl value.  If objc is  less  than
160       or  equal to zero, they return an empty value. If objv is NULL, the re‐
161       sulting list contains 0 elements, with reserved space  in  an  internal
162       representation  for  objc  more  elements  (to  avoid  its reallocation
163       later).  The new value's string representation is  left  invalid.   The
164       two  procedures  increment the reference counts of the elements in objc
165       since the list value now refers to them.  The new list  value  returned
166       by Tcl_NewListObj has reference count zero.
167
168       Tcl_ListObjGetElements returns a count and a pointer to an array of the
169       elements in a list value.  It returns the count by storing  it  in  the
170       address objcPtr.  Similarly, it returns the array pointer by storing it
171       in the address objvPtr.  The memory pointed to is managed  by  Tcl  and
172       should  not be freed or written to by the caller. If the list is empty,
173       0 is stored at objcPtr and NULL at objvPtr.  If listPtr is not  already
174       a list value, Tcl_ListObjGetElements will attempt to convert it to one;
175       if the conversion fails, it returns TCL_ERROR and leaves an error  mes‐
176       sage  in  the interpreter's result value if interp is not NULL.  Other‐
177       wise it returns TCL_OK after storing the count and array pointer.
178
179       Tcl_ListObjLength returns the number of elements in the list value ref‐
180       erenced by listPtr.  It returns this count by storing an integer in the
181       address intPtr.  If the value is not already a list value,  Tcl_ListOb‐
182       jLength  will attempt to convert it to one; if the conversion fails, it
183       returns TCL_ERROR and leaves an error message in the interpreter's  re‐
184       sult  value  if  interp is not NULL.  Otherwise it returns TCL_OK after
185       storing the list's length.
186
187       The procedure Tcl_ListObjIndex returns a pointer to the value  at  ele‐
188       ment index in the list referenced by listPtr.  It returns this value by
189       storing a pointer to it in the address objPtrPtr.  If listPtr does  not
190       already refer to a list value, Tcl_ListObjIndex will attempt to convert
191       it to one; if the conversion fails, it returns TCL_ERROR and leaves  an
192       error  message in the interpreter's result value if interp is not NULL.
193       If the index is out of range, that is, index  is  negative  or  greater
194       than  or  equal to the number of elements in the list, Tcl_ListObjIndex
195       stores a NULL in objPtrPtr and returns TCL_OK.   Otherwise  it  returns
196       TCL_OK  after storing the element's value pointer.  The reference count
197       for the list element is not incremented; the caller must do that if  it
198       needs to retain a pointer to the element.
199
200       Tcl_ListObjReplace  replaces  zero  or more elements of the list refer‐
201       enced by listPtr with the objc values in the array referenced by  objv.
202       If  listPtr does not point to a list value, Tcl_ListObjReplace will at‐
203       tempt to convert it to one; if the conversion fails, it returns TCL_ER‐
204       ROR  and  leaves  an error message in the interpreter's result value if
205       interp is not NULL.  Otherwise, it returns TCL_OK after  replacing  the
206       values.   If  objv is NULL, no new elements are added.  If the argument
207       first is zero or negative, it refers to the first element.  If first is
208       greater  than  or  equal to the number of elements in the list, then no
209       elements are deleted; the new elements are appended to the list.  count
210       gives  the number of elements to replace.  If count is zero or negative
211       then no elements are deleted; the new elements are simply inserted  be‐
212       fore  the  one  designated  by  first.   Tcl_ListObjReplace invalidates
213       listPtr's old string representation.  The reference counts of any  ele‐
214       ments  inserted  from objv are incremented since the resulting list now
215       refers to them.  Similarly, the reference counts for any replaced  val‐
216       ues are decremented.
217
218       Because  Tcl_ListObjReplace  combines  both element insertion and dele‐
219       tion, it can be used to implement a number of list operations.  For ex‐
220       ample, the following code inserts the objc values referenced by the ar‐
221       ray of value pointers objv just before the element index  of  the  list
222       referenced by listPtr:
223
224              result = Tcl_ListObjReplace(interp, listPtr, index, 0,
225                      objc, objv);
226
227       Similarly, the following code appends the objc values referenced by the
228       array objv to the end of the list listPtr:
229
230              result = Tcl_ListObjLength(interp, listPtr, &length);
231              if (result == TCL_OK) {
232                  result = Tcl_ListObjReplace(interp, listPtr, length, 0,
233                          objc, objv);
234              }
235
236       The count list elements starting at first  can  be  deleted  by  simply
237       calling Tcl_ListObjReplace with a NULL objvPtr:
238
239              result = Tcl_ListObjReplace(interp, listPtr, first, count,
240                      0, NULL);
241

SEE ALSO

243       Tcl_NewObj(3),  Tcl_DecrRefCount(3), Tcl_IncrRefCount(3), Tcl_GetObjRe‐
244       sult(3)
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KEYWORDS

247       append, index, insert,  internal  representation,  length,  list,  list
248       value, list type, value, value type, replace, string representation
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251
252Tcl                                   8.0                       Tcl_ListObj(3)
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