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OpenDarwin 7.2.1 - man page for tcl_resetresult (opendarwin section 3)

Tcl_SetResult(3)		      Tcl Library Procedures			 Tcl_SetResult(3)

_________________________________________________________________________________________________

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  refer-
       ence  count is incremented since there is now a new reference to it from interp.  The ref-
       erence 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 concate-
       nation  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 manage-
       ment  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 argu-
       ments 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 vari-
       able 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 asso-
       ciated 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 proce-
       dure 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  applica-
       tions  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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