NAME

       Tcl_NewBooleanObj, Tcl_SetBooleanObj, Tcl_GetBooleanFromObj - store/retrieve boolean value in a Tcl_Obj

SYNOPSIS

       #include <tcl.h>

       Tcl_Obj *
       Tcl_NewBooleanObj(boolValue)

       Tcl_SetBooleanObj(objPtr, boolValue)

       int
       Tcl_GetBooleanFromObj(interp, objPtr, boolPtr)

ARGUMENTS

       int boolValue (in)                 Integer value to be stored as a boolean value in a Tcl_Obj.

       Tcl_Obj *objPtr (in/out)           Points  to  the Tcl_Obj in which to store, or from which to retrieve a
                                          boolean value.

       Tcl_Interp *interp (in/out)        If a boolean value cannot be retrieved, an error message  is  left  in
                                          the interpreter's result object unless interp is NULL.

       int *boolPtr (out)                 Points  to  place where Tcl_GetBooleanFromObj stores the boolean value
                                          (0 or 1) obtained from objPtr.
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DESCRIPTION

       These procedures are used to pass boolean values to and from Tcl as Tcl_Obj's.  When  storing  a  boolean
       value into a Tcl_Obj, any non-zero integer value in boolValue is taken to be the boolean value 1, and the
       integer value 0 is taken to be the boolean value 0.

       Tcl_NewBooleanObj creates a new Tcl_Obj, stores the boolean value boolValue in it, and returns a  pointer
       to the new Tcl_Obj.  The new Tcl_Obj has reference count of zero.

       Tcl_SetBooleanObj accepts objPtr, a pointer to an existing Tcl_Obj, and stores in the Tcl_Obj *objPtr the
       boolean value boolValue.  This is a write operation on *objPtr, so objPtr must be unshared.  Attempts  to
       write  to  a shared Tcl_Obj will panic.  A successful write of boolValue into *objPtr implies the freeing
       of any former value stored in *objPtr.

       Tcl_GetBooleanFromObj attempts to retrieve a boolean value from the value stored in *objPtr.   If  objPtr
       holds  a  string  value recognized by Tcl_GetBoolean, then the recognized boolean value is written at the
       address given by boolPtr.  If objPtr holds any value recognized as a number by Tcl, then if that value is
       zero  a  0 is written at the address given by boolPtr and if that value is non-zero a 1 is written at the
       address given by boolPtr.  In all cases where a value  is  written  at  the  address  given  by  boolPtr,
       Tcl_GetBooleanFromObj  returns TCL_OK.  If the value of objPtr does not meet any of the conditions above,
       then TCL_ERROR is returned and an error message is left in the  interpreter's  result  unless  interp  is
       NULL.  Tcl_GetBooleanFromObj may also make changes to the internal fields of *objPtr so that future calls
       to Tcl_GetBooleanFromObj on the same objPtr can be performed more efficiently.

       Note that the routines Tcl_GetBooleanFromObj and Tcl_GetBoolean are not functional equivalents.  The  set
       of  values  for  which Tcl_GetBooleanFromObj will return TCL_OK is strictly larger than the set of values
       for which Tcl_GetBoolean will do the same.  For example, the value “5”  passed  to  Tcl_GetBooleanFromObj
       will  lead  to  a  TCL_OK return (and the boolean value 1), while the same value passed to Tcl_GetBoolean
       will lead to a TCL_ERROR return.

SEE ALSO

       Tcl_NewObj, Tcl_IsShared, Tcl_GetBoolean

KEYWORDS

       boolean, object