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Tcl_BooleanObj(3)                          Tcl Library Procedures                          Tcl_BooleanObj(3)



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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  writ-ten written
       ten  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 effi-ciently. efficiently.
       ciently.

       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_Get-BooleanFromObj Tcl_GetBooleanFromObj
       BooleanFromObj 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



Tcl                                                  8.5                                   Tcl_BooleanObj(3)