NAME

       Tcl_SetObjResult,     Tcl_GetObjResult,     Tcl_SetResult,     Tcl_GetStringResult,     Tcl_AppendResult,
       Tcl_AppendResultVA, Tcl_AppendElement, Tcl_ResetResult, Tcl_FreeResult - manipulate Tcl result

SYNOPSIS

       #include <tcl.h>

       Tcl_SetObjResult(interp, objPtr)

       Tcl_Obj *
       Tcl_GetObjResult(interp)

       Tcl_SetResult(interp, string, freeProc)

       CONST char *
       Tcl_GetStringResult(interp)

       Tcl_AppendResult(interp, string, string, ... , (char *) NULL)

       Tcl_AppendResultVA(interp, argList)

       Tcl_AppendElement(interp, string)

       Tcl_ResetResult(interp)

       Tcl_FreeResult(interp)

ARGUMENTS

       Tcl_Interp     *interp    (out)     Interpreter whose result is to be modified or read.

       Tcl_Obj        *objPtr    (in)      Object value to become result for interp.

       char           *string    (in)      String value to become result for interp or to  be  appended  to  the
                                           existing result.

       Tcl_FreeProc   *freeProc  (in)      Address  of  procedure  to  call  to  release  storage  at string, or
                                           TCL_STATIC, TCL_DYNAMIC, or TCL_VOLATILE.

       va_list        argList    (in)      An  argument  list   which   must   have   been   initialised   using
                                           TCL_VARARGS_START, and cleared using va_end.
_________________________________________________________________

DESCRIPTION

       The  procedures described here are utilities for manipulating the result value in a Tcl interpreter.  The
       interpreter result may  be  either  a  Tcl  object  or  a  string.   For  example,  Tcl_SetObjResult  and
       Tcl_SetResult  set  the  interpreter  result  to,  respectively,  an  object  and  a  string.  Similarly,
       Tcl_GetObjResult and Tcl_GetStringResult return the interpreter result as an object and as a string.  The
       procedures always keep the string and object forms of the interpreter result consistent.  For example, if
       Tcl_SetObjResult is called to set the result to an object, then Tcl_GetStringResult is  called,  it  will
       return the object's string value.

       Tcl_SetObjResult  arranges  for  objPtr  to be the result for interp, replacing any existing result.  The
       result is left pointing to the object referenced by objPtr.   objPtr's  reference  count  is  incremented
       since  there  is now a new reference to it from interp.  The reference count for any old result object is
       decremented and the old result object is freed if no references to it remain.

       Tcl_GetObjResult returns the result for interp as  an  object.   The  object's  reference  count  is  not
       incremented;  if  the  caller  needs  to  retain  a  long-term  pointer  to  the  object  they should use
       Tcl_IncrRefCount to increment its reference count in order to keep it  from  being  freed  too  early  or
       accidently changed.

       Tcl_SetResult  arranges  for string to be the result for the current Tcl command in interp, replacing any
       existing result.  The freeProc argument specifies how to manage the storage for the string  argument;  it
       is  discussed  in  the section THE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT below.  If string is NULL, then
       freeProc is ignored and Tcl_SetResult re-initializes interp's result to point to an empty string.

       Tcl_GetStringResult returns the result for interp as an string.  If the result was set to an object by  a
       Tcl_SetObjResult  call,  the  object  form  will  be converted to a string and returned.  If the object's
       string representation contains null bytes, this conversion  will  lose  information.   For  this  reason,
       programmers  are  encouraged  to  write  their  code  to  use  the  new object API procedures and to call
       Tcl_GetObjResult instead.

       Tcl_ResetResult clears the result for interp and leaves the result in its normal empty initialized state.
       If  the  result  is  an  object, its reference count is decremented and the result is left pointing to an
       unshared object representing an empty string.  If the result  is  a  dynamically  allocated  string,  its
       memory  is  free*d and the result is left as a empty string.  Tcl_ResetResult also clears the error state
       managed by Tcl_AddErrorInfo, Tcl_AddObjErrorInfo, and Tcl_SetErrorCode.

OLD STRING PROCEDURES

       Use of the following procedures is  deprecated  since  they  manipulate  the  Tcl  result  as  a  string.
       Procedures  such  as  Tcl_SetObjResult  that manipulate the result as an object can be significantly more
       efficient.

       Tcl_AppendResult makes it easy to build up Tcl results in pieces.  It takes each of its string  arguments
       and  appends  them  in  order  to  the  current  result  associated with interp.  If the result is in its
       initialized empty state (e.g. a command procedure was just invoked or Tcl_ResetResult was  just  called),
       then Tcl_AppendResult sets the result to the concatenation of its string arguments.  Tcl_AppendResult may
       be called repeatedly as additional pieces of the result are produced.  Tcl_AppendResult takes care of all
       the  storage  management  issues  associated  with  managing interp's result, such as allocating a larger
       result area if necessary.  It also converts the current interpreter result from an object to a string, if
       necessary,  before  appending  the  argument  strings.  Any number of string arguments may be passed in a
       single call; the last argument in the list must be a NULL pointer.

       Tcl_AppendResultVA is the same as Tcl_AppendResult except that instead of taking  a  variable  number  of
       arguments it takes an argument list.

       Tcl_AppendElement  is  similar  to  Tcl_AppendResult  in that it allows results to be built up in pieces.
       However, Tcl_AppendElement takes only a single string argument  and  it  appends  that  argument  to  the
       current  result  as a proper Tcl list element.  Tcl_AppendElement adds backslashes or braces if necessary
       to ensure that interp's result can be parsed as a list and that string will  be  extracted  as  a  single
       element.   Under  normal conditions, Tcl_AppendElement will add a space character to interp's result just
       before adding the new list element, so that the list elements  in  the  result  are  properly  separated.
       However  if  the  new  list  element  is the first in a list or sub-list (i.e. interp's current result is
       empty, or consists of the single character ``{'', or ends in the characters ``  {'')  then  no  space  is
       added.

       Tcl_FreeResult  performs  part  of  the  work of Tcl_ResetResult.  It frees up the memory associated with
       interp's result.  It also sets interp->freeProc to zero, but doesn't change interp->result or clear error
       state.   Tcl_FreeResult  is most commonly used when a procedure is about to replace one result value with
       another.

DIRECT ACCESS TO INTERP->RESULT IS DEPRECATED

       It used to be legal for programs to directly read and write interp->result to manipulate the  interpreter
       result.   Direct  access  to  interp->result  is now strongly deprecated because it can make the result's
       string and object forms inconsistent.  Programs should  always  read  the  result  using  the  procedures
       Tcl_GetObjResult or Tcl_GetStringResult, and write the result using Tcl_SetObjResult or Tcl_SetResult.

THE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT

       Tcl_SetResult's  freeProc  argument  specifies how the Tcl system is to manage the storage for the string
       argument.  If Tcl_SetResult or Tcl_SetObjResult are called at a time when interp holds a  string  result,
       they  do  whatever  is necessary to dispose of the old string result (see the Tcl_Interp manual entry for
       details on this).

       If freeProc is TCL_STATIC it means that string refers to an area of static storage that is guaranteed not
       to be modified until at least the next call to Tcl_Eval.  If freeProc is TCL_DYNAMIC it means that string
       was allocated with a call to Tcl_Alloc and is now the property of the  Tcl  system.   Tcl_SetResult  will
       arrange  for  the  string's  storage  to be released by calling Tcl_Free when it is no longer needed.  If
       freeProc is TCL_VOLATILE it means that string  points  to  an  area  of  memory  that  is  likely  to  be
       overwritten  when  Tcl_SetResult  returns  (e.g.  it points to something in a stack frame).  In this case
       Tcl_SetResult will make a copy of the string in dynamically allocated storage and arrange for the copy to
       be the result for the current Tcl command.

       If  freeProc isn't one of the values TCL_STATIC, TCL_DYNAMIC, and TCL_VOLATILE, then it is the address of
       a procedure that Tcl should call to free the  string.   This  allows  applications  to  use  non-standard
       storage allocators.  When Tcl no longer needs the storage for the string, it will call freeProc. FreeProc
       should have arguments and result that match the type Tcl_FreeProc:
              typedef void Tcl_FreeProc(char *blockPtr);
       When freeProc is called, its blockPtr will be set to the value of string passed to Tcl_SetResult.

SEE ALSO

       Tcl_AddErrorInfo, Tcl_CreateObjCommand, Tcl_SetErrorCode, Tcl_Interp

KEYWORDS

       append, command, element, list, object, result, return value, interpreter