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Tcl_SetResult(3)                           Tcl Library Procedures                           Tcl_SetResult(3)



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NAME
       Tcl_SetObjResult,  Tcl_GetObjResult, Tcl_SetResult, Tcl_GetStringResult, Tcl_AppendResult, Tcl_Appen-dResultVA, Tcl_AppendResultVA,
       dResultVA, 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  argu-ment; argument;
       ment;  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  point-ing pointing
       ing  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.  Pro-cedures Procedures
       cedures 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 argu-ments arguments
       ments 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 inter-preter interpreter
       preter 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 neces-sary necessary
       sary 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  inter-preter interpreter
       preter  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 pro-cedures procedures
       cedures  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



Tcl                                                  8.0                                    Tcl_SetResult(3)

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